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kevinscar

Hard Starting 350

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Next problem I'm working on with my 35 hot rod is bad starting once the engine is hot. The engine is a 350 and I believe it's from a 1990s Chevy (not sure of the donor vehicle). It's not fuel injected, just an old carb. Here's the symptoms:

- Car is difficult to turn over when cold but it does start

- After 5 minutes of running, car starts right up if you turn it off

- After 10 minutes, if you turn off the car, it's almost impossible to start. Let set 15 minutes, it starts as if cold.

I have replaced the battery, starter (put a high torque on there) and I've put a heat shield around the starter. Nothing seems to make all that much of a difference.

One thing with this car, it has a battery disconnect that has to be disconnected whenever the car sits or the electric fan just continues to run (yes, they got some sort of wiring problem). I don't think that's taking enough out of a fairly new yellow top optima to prevent starting. The fan never does turn off though.

Any thoughts?

Thanks!

Edited by kevinscar (see edit history)

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One thing that I would check first is how well your electrical system is grounded. Very often a bad ground will inhibit or slow starting. Just a thought.

Rog

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Okay, had to put this project on the shelf for a few months, and finally got back to it a couple of days ago and I'm stumped. I hope people can follow this... might be confusing. Here is what I have done so far.

1) I have put a heavy ground strap from the battery (in the trunk) to the frame of the car

2) I have replace the battery with a new heavy duty 1000 cranking amp battery

3) I have put a heat shield on the starter

4) Checked the timing (looks very good)

Still, the car will start hard when warm.

I've traced the wiring from the battery to a cutoff switch under the dash. This switch, I was told, needs to be turned off whenever the car is sitting because the battery will drain (seems to me a wiring problem). It is a normal cutoff switch, but instead of cutting off ground, they cut off the 12V to the starter.

The 12V lead from the cutoff switch goes to the starter solenoid as expected. On the starter solenoid you will find the 12 V from the cutoff switch and two other leads. On inspection, both these leads are connected to the post on the alternator. If you check these leads they are at 1.2 Ohms. Seems wrong to me. So, basically this is telling me that I have 1.2 Ohms to ground at the back of the alternator and on the starter.

I took these leads off the alternator and traced them. One lead (black) goes only between the starter and the back of the alternator. It seems this lead is used to recharge the battery?

The other lead (white) goes through the firewall and into the fuse panel. This is where we are picking up 1.2 Ohms. The 1.2 Ohms is the load resistence of the radiator fan.

So, here's what I'm thinking.

1) I have to assume that the black lead between the alternator and the starter is used to charge the battery. It's a pretty small gauge wire, not near as big as the one in my jeep (which btw, goes directly from the alternator to the battery).

2) The fan lead is in the wrong place. It needs to be taken off the back of the alternator and re-located to another supply.

For an experiment, we did try to remove the fan lead, but our new battery was already so drained that we were down to 9V while cranking. Figured I'd call it a night.

Am I on the right track?

Advice would be appreciated.

Thanks in advance!

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The fact there's a cut-off switch on the power lead is very suspicious to me -- period! Kind of sounds like somebody wired something where it shouldn't have been, then used the switch to correct their error?

For a wiring diagram you might be able to work off of . . .

Camaro Wiring & Electrical Information

This should bring up a wirning diagram page. In the '74-'77 column, click on "Engine Bay". That'll give you a factory schematic which you can print . . . color codes and everything. Click the "+" cursor to get a bigger version. The "Engine/Forward Lamp" diagram might be a little easier to read, though.

In ALL starter circuits, there should be a fusible link to protect the circuit, much like an inline fuse, except it's hidden in a wire. A black wire, generally about the size of a 10 gauge wire with "grainy" black insulation, but is softer internally and externally. Some Camaros in later years had TWO lengths of it, run in parallell. The factory wiring diagram should have ONE of them in it.

Regarding the battery in the trunk . . . back in the early 1960s when many SuperStock drag racers first did this, the biggest battery back then was no where near the CCA of the battery you have now AND they still cranked well. KEY THING is to make sure the power cable from the battery to the front of the car is as large as it can be . . . welding cable is a more recent choice for many racers with this set-up. This ensures that MINIMAL power is consumed by the longer run of the power lead, compared to an underhood mount battery. But then too, later model Cadillac DeVilles have the battery under the back seat and they don't have quite that large of a power lead. BUT, in this case, bigger is usually better.

As for the electric radiator fan, NO WAY should it be wired direct. It should be modulated by a separate temperature sensor on the engine. ONLY running when the engine coolant temp need it--period! It's not unusual for OEM fans to run after the engine is turned off, until the temp decreases to lower levels. With a larger battery on modern vehicles, they DON'T run the battery down even if they run 30 minutes.

As for the hard starting . . . this can be problematic. All I can suggest is that you make sure the starter drive is correctly positioned from the flywheel. This is where the famous starter shims come in, possibly! I consider them a bandaid-fix, though, AND a fix which can be problematic. In theory, the starter drive gear should go only about 1/2 the way into the flywheel's ring gear teeth. I believe the factory spec is about .035" between the deepest part of the ring gear's teeth and the outer tip of the starter drive's teeth. BUT, you'll know when it's correct by the way it sounds and acts.

The heat shields come in various sizes and shapes, whether it's factory or aftermarket. Some look marginal (the factory ones), but they seem to work. What IS highly advisable is to put the "end brace" on the starter. In starter-to-block mounting, you have the two main starter bolts (which have starter-specific knurlings on their shank near the bolt head). These work reasonably well, BUT if you have an engine which is of higher compression or such, then the factory "end brace" is HIGHLY ADVISABLE. This brace goes between the end of the starter (usually the stud that sticks out of the main housing) and a close-by tapped hole in the cylinder block. It firmly anchors the starter to keep it completely immobile and in position at all times. If the main two bolts might get a little loose, or even ONE of them, then the starter housing can kick and rotate on one of the bolts. End result is compromised gear teeth engagement between the starter and the flywheel ring gear . . . ultimate result could be a broken starter drive end housing, or in the case of diesels, cracked-out bolt holes in the block.

One other little detail, which might not be that significant, but some might consider it such. On the end of the starter solenoid where it attaches to the lug from the starter windings, is there a cylindrical spacer between it and the lug or does the lug attach directly to the solenoid? IF the spacer is needed, then you have the "HD" starter, or the one with the longer main body which is "higher torque" than the normal starter. Some people swear by the bigger starter, but it does seem to last longer in many cases. This is for the GM-ACDelco OEM starter from back then.

Other than this, make sure that ALL of the electrical connections are clean and dry. In ALL cases, use a flat washer and/or star washer between the terminals and what they attach to. This puts an intermediary surface between the bolt/nut head so you don't twist the terminal as you tighten the nut/bolt that holds it together. On the starter terminals, I think they used small lock washers?

When you mention "Hard to start", is that like the engine turns over slowly or it has "extended crank time"? The former would relate to voltage issues in the starter circuit, but the latter would relate to fuel/spark issues.

As your vehicle seems to have some things done to it by undetermined individuals, I suspect that if you take the factory wiring diagrams and trace things out, you'll probably find and correct your issues.

ALSO, don't forget to check the bulkhead connector for poor interface of the various connectors. From my own experineces, make completely sure the battery cable connections/terminals are clean and shiney where they touch. I did an electronic ignition conversion on my '67 Chrysler. After it was completed, I started it to see if it would work. I did 4 starts in a row, but the 5th one was "dead". I was getting voltage everywhere it should be, but "no start". The battery cable terminals on the top post battery looked to be good and tight, BUT when I took them apart, there was a thin layer of gunk on the inside of the cable ends and on the terminal posts. I found a battery terminal brush I'd gotten as a door prize a few years prior and cleaned the contact points. It looked insignificant, but it WAS highly significant. End of problem until I found the main lead power wire in the bulkhead connector had a loose connector . . .

Key thing is to systematically and calmly follow the factory wiring diagrams. You might also need to look at the instrument panel diagrams to see what's on the passenger side of the bulkhead connector. Also make sure all grounds between the engine and body as in place . . . like the ones which normally went from a rear bolt of the valve cover hold-down or screwed into the back of the cylinder head that went to the cowl. Otherwise, you can get some back-feed voltage which can cause still other problems!

Keep us posted, please.

NTX5467

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Wow, tremendous amount of information.

You are right, something is wired wrong - that's why the cutoff switch is in there. Without it being "off" the battery would drain when the car sits.

Unfortunately this is going to sit for another few days. Had to move it out last night due to my son's jeep having some issues. Figure he will get that done this weekend and I can start again next week.

One thing you didn't comment on was the small connection between the alternator and the starter solenoid's lead to the battery. I was thinking of removing that and just running a heavy gauge wire directly to the battery from the alternator.

My next test was going to be to pull the battery from the trunk and mount it next to the starter with a very short heavy cable. I'll mount the fan leads to a different battery (it's isolated) so as to keep the engine cool. I figured, this way, I'd bypass all the wiring between the trunk, the switch and the starter (and who knows where else it goes). Will also pay attention to the depth of the starter teeth to determine if shims are required. Will also take a look for the cylinderical spacer your mentioned. This is supposed to be an HD starter (NAPA), so I anticipate I should see it based on your description.

You mentioned a fusible link, but I see absolutely none. I've always wondered... why a fusible link and not just a fuse? I suspect you know.

When it is hard to start, it is slow cranking. It's as if the starter doesn't have the power to turn the engine over (as if the compression is preventing it). Also, when it is hard to start, each time I checked the battery voltage when I'm cranking and every single time the battery voltage drops at least 2.5V to 3V. When the battery is fully charged, I don't think I ever saw more than a 1V drop during cranking. This is why I was also suspecting that charging circuit.

So, here's what I was thinking. The battery is never properly re-charging due to the small gauge wire between the alternator and the battery. When I start the car the first time, I have full battery power. However, after 20 minutes of run time, the battery power has diminished to the point that it no longer has the power to turn over the hot starter/engine. When I try to start it hot, I can guarantee a 2.5V to 3V cranking drop. I am thinking that the battery power is diminished because the fan is constantly running and if that alternator circuit is not recharging the battery fast enough, the battery will run down. It's not run down enough to measure something less than 12V while sitting... but when cranking, that 2.5V to 3V drop just isn't right (and this is now a new red top optima).

Your advice is excellent. Man, I wish I had the internet 30 years ago when I was working on my camero!!

Will keep you posted. Thank you very much!

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I suspect the fuse link wire is there due to it being tougher to hurt than a glass fuse would have been if exposed to the same environment.

The wiring schematic will reference the wire gauge in the description and color codes, usually.

While you're checking things, I think I'd get the alternator output checked. "On the car" is usually the best way. Plus a load check on the battery, AFTER it's been charged with an automatic charger (probably out of the car). Even if they are "to specs", then you'll know that they are, as a baseline.

Take care,

NTX5467

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Okay, got a chance to work on the car for a few hours today.

Read back thorough the suggestions and verified things look good outside of the connections. Starter seems to engage good. I decided to take NTX advice and now follow the hot lead to the battery... and holy cow. The hot lead goes from the trunk, under the passenger side of the car and up the firewall. It then goes through the firewall where it is spliced to another section going under the dash over to the cutoff switch. Loose leads were found on the cutoff switch. I then decided I should just try my test and bypass all the wiring that was done from the battery to the starter. I put two short leads (one ground one 12V) to the battery and set the battery right outside the engine compartment. The engine fired strong. I let it sit for about 15 minutes (engine temp was about 210) and turned it off. Cranked it over again and started strong. Did this several times, each time it started strong. I think I found the problem. Let it run for a while, turned it off and it started strong again! I figured I had it... one more time. I turned it off... cranked it over and it hard started!!! I had my son measure the voltage across the battery and the voltage dropped to 9V when cranking. I hooked up a charger on jumpstart and it cranked right over. Started beautifuly. Seems the battery is now not getting charged.

I'm suspecting I had a couple of problems. I solved the poor connection problem and now I am thinking that the alternator is just not doing it's job (either a connection or bad alternator). I measured the voltage at the back of the alternator several times and it seemed to go anywhere from 12.3v to 13.5v. It was not consistent. The battery voltage always matched the alternator.

I also pulled the negative lead to the battery while the engine was running (this engine has no computer) and the fan turned, but slow! I didn't put the lights on.

Was thinking of pulling the alternator and having it tested. Seems like the small wire to the alternator is okay.

Thanks again for the advice. Always learning!

Edited by kevinscar
update (see edit history)

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Thanks for the update! Looks like things are getting sorted out very nicely.

Take care,

NTX5467

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Okay, took the alternator in and it was bad. Got a new one, put it in and things were looking good. Started it up strong, let it run for a while, then turned it off and started it again. Things were looking very good. Went to show my son and turned it over again... damn! Another hard start! Checked the battery voltage and once again, dropping to 9v while cranking. I do have the heat shield off the starter...

On the bright side, it does start a heck of a lot better than before, just not 100% yet.

Ugh!

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Okay, it's been a long time since I've been working on this car. My son and his buddies have completely consumed all available hours in my shop for the past several months. My son tells me the other day that he'd like to take the hot rod to prom and I said "sure, as long as you help me get it in the shop and finish up on the starter". He and his buddies cleaned things up and we got it into the shop. It started beautifully every time (my son said about 30 times). He's confident it's fixed. I said "I am not so sure". It still hard cranks when hot but at least it does not fail to start like it use to. My son said said he could guarantee if the engine sounds like it's turned over a max of 8 times, all of a sudden it will just grab and start right up.

Gets back to a question I had eariler...

Could the compression after it's started be so high that there are problems starting it until we've cycled through all the cylinders? My plan for figuring out the final bugs in this is to go through NTX's recommendations again and make sure I covered them all, but if it's compression, I'm not sure I've got a clue. BTW, the timing is spot on.

Thanks!

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Finally, I believe we have success! It was several problems that were biting us in this hard starting issue. I'll go through the list:

1) parasitic current drain on the battery (so the battery was never fully charged). We found out that the lights for the power windows stayed on 24x7... and so the battery was never fully charged to begin with.

2) Bad alernator. I took it in and it was tested bad. Replaced the alternator. Once again, battery was never re-charged properly.

3) Loose lugs on the power cutoff switch. I re-wired the hot lead to the trunk battery to be direct. Cutoff is no longer necessary given we no longer have a parasitic current drain.

4) Hot starter - I don't really know if this was an issue or not, but I now have a heat shield on it.

5) Very tight flywheel/starter meshing. I took NTX's advice and shimed the starter a little. I can't honestly say that I know for a fact that it was a problem, but from what I read, the gears were meshed too deeply. We pulled it back out a small amount.

6) Poor connection from alternator to battery for re-charge. Even after we replaced the battery and the alternator, the voltage at the battery was always less than the output of the alternator. Alternator was putting out 13v when the engine was running . We replaced the small wire that was originally to the battery with a beefy 2 gauge wire.

Starts now, 100% of the time. Occasionally, we get a slow crank, but nothing like we had before. My son is happy and I enjoyed a nice cool beer once it was done.

Thanks for the advice. I appreciate the time you guys take to help noobs like me out.

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Thanks for the update! Now that it's doing better and reliably so, the next thing would be to ensure that the sparks happen quickly while trying to start it.

When it has heat soaked, is there still fuel in the float bowl? Does the accelerator pump shoot a solid stream "first time"? Is the carb base gasket a "thicker" one or is it a thin one? If you took the air cleaner off after the hot soak, do you see wetness in the venturi area or smell gasoline? What does the temp gauge read for engine temp during the slower cranking time?

For the ignition . . . what type of distributor is on the motor? Points? Electronic? HEI?

What kind of spark plugs? Brand and heat range number? What type of condition? Gap?

Lastly . . . how much throttle is being used during these cranking times? Just a little? 1/3? 1/2? More??? What about idle speed and mixture adjustments?

Key orientation is that if the spark plugs are sparking sufficiently during these hot cranking times, they should be sparkling enough for the engine to fire off quickly. I suspect that making sure that is happening might shorten the existing cranking time when hot.

Just some thoughts,

NTX5467

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Thank you! Will go thru the list as you recommend. Still starting every time but sometimes turns over hard and slow for at most 8 cycles. Never more than 8. After 8, the crank is always strong and the car starts right up.

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Been thinking about going through the list NTX provided... doing a bit of reasearch. Correct me if I'm wrong... but here's what I am thinking.

While we may have an issue with the spark efficiency (and I will verify this), spark efficiency would not cause a slow crank would it? If the spark efficiency was improved from let's say 60% to 100%, I would bet the crank would still be slow, but the engine would start quicker as opposed to requiring 8 cycles in many cases.

Thanks in advance!

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I just noticed that your battery was in the trunk! I tried this (for weight distribution) on one of my cars. Used 4/0 copper cables, ground cables, large battery, etc., etc., etc. Generally, it worked. Occasionally, it DIDN'T work when hot (slow or no cranking).

I finally gave up, relocated the battery to the engine compartment, ZERO problems since regardless of ambient temperature and/or how soon after shutoff we tried to refire the engine. Just too long a run for 12 VDC.

Jon.

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I just noticed that your battery was in the trunk! I tried this (for weight distribution) on one of my cars. Used 4/0 copper cables, ground cables, large battery, etc., etc., etc. Generally, it worked. Occasionally, it DIDN'T work when hot (slow or no cranking).

I finally gave up, relocated the battery to the engine compartment, ZERO problems since regardless of ambient temperature and/or how soon after shutoff we tried to refire the engine. Just too long a run for 12 VDC.

Jon.

Jon,

I considered that, but even when I had the battery pulled and mounted next to the engine on shorter 2 ga battery cable, I still hard cranked. You know, I have to admit, when I was doing that, I was uncovering so many other issues. I haven't tried it now that it starts every time now. I could maybe try it again, it's a pretty simple test. The unfortunate thing is that the engine compartment has little/no space for mounting a battery.

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Been thinking about going through the list NTX provided... doing a bit of reasearch. Correct me if I'm wrong... but here's what I am thinking.

While we may have an issue with the spark efficiency (and I will verify this), spark efficiency would not cause a slow crank would it? If the spark efficiency was improved from let's say 60% to 100%, I would bet the crank would still be slow, but the engine would start quicker as opposed to requiring 8 cycles in many cases.

Thanks in advance!

Correct. I was thinking that if the crank time might be decreased, it might make the slow turn-over less of an issue. More like "rump -- rump -- VROOOM".

The eight revolutions of cranking kind of make it seem like an evaporated fuel issue, as it might take 8 revolutions for the fuel pump to get sufficient fuel back in the float bowl for the engine to fire and run reliably.

Please keep us posted . . .

NTX5467

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Correct. I was thinking that if the crank time might be decreased, it might make the slow turn-over less of an issue. More like "rump -- rump -- VROOOM".

The eight revolutions of cranking kind of make it seem like an evaporated fuel issue, as it might take 8 revolutions for the fuel pump to get sufficient fuel back in the float bowl for the engine to fire and run reliably.

Please keep us posted . . .

NTX5467

Explains why you wanted me to check the float bowl. Maybe can get to that once the rain stops. It's a lot easier to see outside. If the float bowl is out of fuel, is that because the fuel pump turns off but the engine is still consuming fuel at shut down? My son has a built jeep and he actually has a separate switch for his fuel pump on an LQ4 engine. Of course, that's a fuel injected engine.

So, my next steps are to play again with the battery cable length and go through the list you suggested. Would a dual battery setup help if cable length is an issue or is it just the current carrying capacity of the cable itself? I have an optima battery with 1000 cranking amps in back.

Thanks!

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Once the engine stops, fuel consuption stops, too.

Suspecting that possibly the added (evaporation tendencies) volatility of modern fuels might cause "percolation" of the fuel after the engine stops and the carb absorbs more engine heat.

Modern-style fuel injected engines have to have an electric fuel pump--period. There has to be a certain level of fuel pressure for the injectors to fire and the engine to start. In OEM applications, it all happens with the turn of the ignition key. With adaptations into other vehicles, then some manual switches are required.

Back when the serious drag racers started to put their heavy batteries in the trunk, near the rh rear tire, for alleged better traction, they used batteries (circa 1962) that were about 1/2 as powerful as your 1000A/hr Optima battery. They generally used welding cable rather than the normal-size battery cables of that time. The much larger cable is needed to prevent or minimize voltage loss in the cable, due to its length.

Back in the middle 1960s, up to about 1970, it was not that uncommon to see a nice Chevy II (or other hot rod Chevy) that looked great, but was obviously upgraded under the hood. Bigger carbs, "more" camshaft, higher compression, etc. MANY of them didn't start too easy, but only with about 2 or 3 slow revoluations before the engines fired-off. Even with the batteries in the underhood area. If, for some reason, it didn't start by about the 5th turn-over, it was jumper cables time.

I know there was some good explanation for this situation, but they all didn't do it. Back then, it sounded like the battery was just weak, but I'm sure the owner would claim it was the high-compression ratio, bigger cam, or whatever that made it that way . . . as if the slow start was a "Badge of Honor" for a "hot rod". Or it might have been that he couldn't afford premium fuel, so he had the timing retarded so it didn't clatter too bad on regular?

Any progress and updates?

Just curious,

NTX5467

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I sincerely appreciate all the information you are providing. This is such a good explanation (I've referred my son to these writeups too).

Since I was last on, I've not been able to get to do anything with the hot rod. Between weather and work, I've got a full plate. However, my son is taking it to Prom this weekend. Like I said eariler, I no longer worry about it not starting, I just am concerned about the hard slow cranks when hot. It appears to me that you have, several times, pointed out that hard slow cranks is not such a big deal as long as you have fuel in the carb and an effective spark. I was going to play with the timing a little bit once we got it out, but potentially I should just focus on the fuel delivery (and possible evaporation). I don't know that I will get to it this weekend, but I am itching to dig in again.

Once again, I really appreciate all the time you take to carefully explain things. It's been extremely helpful. I will certainly provide an update when I next dig in.

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