Exhaust Manifold "SPARKING"

[R.White]

This afternoon I set the timing so that the mark on the flywheel was centred in the inspection window with No.1 on compression and cleaned the area then highlighted the line with white paint. I then checked that No.1 plug lead aligned with the rotor arm and with the plug reinstalled I attached the timing light to that lead with my 12 volt battery as a power source. With the manual advance/retard lever fully retarded and the tick- over set at a moderate rate the line appeared steady in the centre of the hole. By increasing the revs, the line moved away from the centre but still remained steady. The strobe light seemed to remain steady under all conditions, on all leads, except that I had not taken the car out so until I have done at least a mile, I doubt the power loss and tailpipe backfire up will present itself. I think the engine needs to get properly warmed through before the symptoms can be identified.

Ray.

[TexasJohn55]

Ray, check all plug wires just for grins at speed before you drive it, you might get lucky and catch it skipping. Same on road test, if it starts missing but the strobe is consistent, move to another wire.

[R.White]

I have just been out in the car and it was backfiring after a few minutes. I returned to my garage and within the gloom I noticed sparks coming from the exhaust manifold again!!!! This time the sparks were infrequent and red in colour. By now I was revving quite hard - but NO BACKFIRE and eventually, NO SPARKS. With the ignition fully advanced and the engine hot there was no sign of any skipping of the spark with the strobe, so I thought I would take it out again..... but I have been stopped in my tracks by a leak from the water pump. At least it happened in the garage and not out on the road.

Ray.

Edited June 4, 2013 by R.White (see edit history)

[TexasJohn55]

Respectly re-submitted for consideration.

Run a ground strap from the manifold to whatever it is sparking to.

Edited June 4, 2013 by TexasJohn55 (see edit history)

[R.White]

I may not have been clear, John. The sparks have not been going anywhere. They are just shooting outwards into the air from the casting. I am not sure what it is but they could just be iron filings from when I filed the worst of the repairs down, the draft from the fan at high revs lifting them away very hot and causing a spark to fly. The short from the distributor, on the other hand, is most definitely a problem that Dodge recognised and I have grounded the casing and it no longer sparks there.

What do you think about the idea that the backfire could be down to a heavily carbonated cylinder head? I once had an old Ford which would backfire but with a decoke ran O.K. When I ran the engine hot at high revs this afternoon it seemed to blow away the cobwebs. Just wishful thinking?

I will need to stem the water pump leak before test driving the car again.

Thanks for your help.

Ray.

[TexasJohn55]

What do you think about the idea that the backfire could be down to a heavily carbonated cylinder head? I once had an old Ford which would backfire but with a decoke ran O.K. When I ran the engine hot at high revs this afternoon it seemed to blow away the cobwebs. Just wishful thinking?

I will need to stem the water pump leak before test driving the car again.

Thanks for your help.

Ray.

Nope, that would cause preignition and pinging but I doubt backfire. Strobe your wires under load after you get your water pump fixed, I would like to know what the problem really is before you throw on all them new parts. If they fix it, which part was at fault? Humor me here. John

[R.White]

I will be sure to strobe the wires again under load if the problem persists but this afternoon the backfire went away of it's own accord with persistent high revs. If it never happens again then we may never know what has been causing it.

I don't get that lucky.

Could weak valve springs cause mixture to be forced into the exhaust and backfire?

Ray.

[ply33]

An exhaust manifold leak can cause back firing, especially on deceleration. If I understand correctly, the manifold on your car has been welded or brazed. Maybe it was put together a little out of alignment and the gaskets can't fully seal it against the block. . .

[TexasJohn55]

Weak valve springs would cause it to miss at high rpm, not likely just under a load at moderate rpm. I assumed it was dictated by load at normal rpms not overrevving. So is it only high rpm related? Something I dared not mention before is a flat cam lobe, but that is usually associated with backfire through the intake from bad exhaust lobe. If intake lobe flat, it just couldn't get a good charge of air and fuel, it would miss or fire weakly and set up a shudder but not sure if it would backfire out the exhaust. A backfire is nothing more than delayed ignition of fuel/air mixture in the exhaust after leaving the engine. There should not be a volatile mix in the exhaust unless ignition was interrupted or delayed. John

[R.White]

An exhaust manifold leak can cause back firing, especially on deceleration. If I understand correctly, the manifold on your car has been welded or brazed. Maybe it was put together a little out of alignment and the gaskets can't fully seal it against the block. . .

This is quite possible. Occrj has had his manifold machined because of this very problem and if this is the same as mine, it will also need to be done. I have my suspicions and will have to check it out. This has been discussed from post #30 in my thread "Unusual problem" (when I thought the problem had been resolved by fitting a new coil) and we talked about the difficulty of finding suitable gaskets.

The backfire was happening under load when driving along and replicated by high revving in my garage. There has not been a noticeable miss fire at any speed or r.p.m. so it's probably not valve bounce.

Ray.

[Ron Lawson]

Ray Just a queery Your motor hasn't got a guts full of carbon has it This will cause all the symptons that you are having with the back firing

[TexasJohn55]

And the concurrent loss of power?

[R.White]

Hi Ron, I suspect there is a build up of carbon judging by the state the plugs were in when I first removed them and the carb was set far, far too rich. If I prod the top of a piston with my finger, it is bringing out loose carbon so I thought, like you, that it needs a decoke at the very least. I wouldn't think the backfire could produce sufficient back pressure to disrupt power as much as it does - as if there is a fuel starvation issue or ignition switch or coil/king lead failure; and there is really plenty of power and no problems until I have driven for about a mile. If I leave the car for a short while, it starts up fine and does another short trip before playing up again. As if it's a heat related issue. <br>

<br>

By the way, Ron, if you get to the parts store again, please can you look for a '26 water pump - I need a good core to rebuild. Thank you.<br>

<br>

Ray

Edited June 5, 2013 by R.White (see edit history)

[R.White]

April 16th, 2013 #30 <!-- google_ad_section_start(weight=ignore) -->R.White<!-- google_ad_section_end -->

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'26 Touring

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<dl class="userinfo_extra"><dt>Join Date</dt><dd>Sep 2011</dd><dt>Location</dt><dd>Derby, England. (G.B.)</dd><dt>Posts</dt><dd>1,154</dd></dl>

[h=2]<!-- google_ad_section_start -->Re: Unusual problem<!-- google_ad_section_end -->[/h]

<!-- google_ad_section_start -->Unfortunately my manifold branches have worn very thin around their mating edges and I feel the crush rings would be too thin to make a reliable seal. There is always the option of using the felt type but I prefer something a little more substantial. Fortunately, Yamaha 250/350 motorbike exhaust gaskets have a flat mating surface and an internal diameter of 43mm, external 53mm, and are just the ticket!

Someone has welded on a three point flange to take that type of exhaust down pipe. I shall not alter this and now I have relieved the surplus weld from around the holes, I can now use the correct size bolts to attach it.

Ray.<!-- google_ad_section_end -->

[R.White]

I suppose it could always be the new coil breaking down. It wouldn't be the first time new parts have been duff!

Ray.

[R.White]

I have just taken the car out again and now the problem is worse than ever. After leaving the car ticking over for 20 minutes with revving the engine and no sign of trouble, the cutting out and tailpipe backfire is happening as soon as the car gets under load. pulling the choke or altering the advance/retard makes no difference.

Obviously I have a problem which is difficult to diagnose. It will take some time to resolve but I expect the problem will get sorted out eventually.

Thanks everyone; I will post any developments.

Ray.

[Guest 1930]

http://forums.aaca.org/f143/exhaust-manifold-sparking-351889-3.html#post1177587

Go up to the top Ray, ( address bar ) left click, itll turn blue, right click, scroll down to copy, click on that, go to your reply and right click again, scroll down to paste, left click that, it will then show up here.

[R.White]

Thanks Jason. I am with you and understand how to copy and paste as you describe. What I was also hoping for was a way to direct readers to another site by simply including the word "here" (shown in blue) in the middle of a sentence instead of pasting the whole http address. I have seen this done on another forum and asked for an explanation but none was forthcoming. Of course, it may depend on what software you have but I am often out of my depth with computers.

Ray.

[R.White]

I suppose it could always be the new coil breaking down. It wouldn't be the first time new parts have been duff!

Ray.

No, the new coil is fine. I tried out the coil and king lead on my vintage Austin and it was fine.

At least that is something else I can eliminate.

Ray.

[TexasJohn55]

Ray, humor me a minute, ok? When you checked strobing in the garage when it was missing or backfiring, did you check all plug wires individually? Are you using an inductive pickup timing light? Much easier than direct connect and no chance of connection causing spark jump to ground. Have you checked all plug wires under load? John

[R.White]

I can try to humour you, John (but I don't seem to have a great deal to laugh about!)

I had the light attached to each lead in turn and with the engine running at various different speeds saw no break in the light regularity. I believe I have given an account of how I checked the timing and found the line to remain steady. The engine shows no sign of missing until out on the road; particularly under load. Then it seems to die and backfire; go along a bit then die and backfire again. Sorry, I don't know what an "inductive" timing light is. My light is connected directly to the lead and has never given trouble. Also, how do you check plug wires under load? I am working alone, so no help here.

If I place the palm of my hand near to the exhaust exit I can feel regular pulses of pressure but occasionally there is a cough.

Ray.

Edited June 5, 2013 by R.White (see edit history)

[Guest 1930]

Thanks Jason. I am with you and understand how to copy and paste as you describe. What I was also hoping for was a way to direct readers to another site by simply including the word "here" (shown in blue) in the middle of a sentence instead of pasting the whole http address. I have seen this done on another forum and asked for an explanation but none was forthcoming. Of course, it may depend on what software you have but I am often out of my depth with computers.

Ray.

The way I understand it is that depending on forum software sometimes you will see HERE and sometimes you will see the entire Url, it seems to be something out of your control but either way it will provide the needed link

[R.White]

I believe you are right Jason and it's down to software.

Getting back to the thread.

Do you have an opinion based on your own experience about what I should do to fix my car.

[Guest 1930]

Buy a 29

[R.White]

:oGuess I asked for that!

[Guest 1930]

Kidding, if I were there with you Ray we would have it in top running order, VERY frustrating trying to throw suggestions at something that I cannot see and lay my hand, I have complete confidence you will however find your answers Ray.

[R.White]

Cheers Jason. Goodnight from me now.

Ray.

[TexasJohn55]

I can try to humour you, John (but I don't seem to have a great deal to laugh about!)

I had the light attached to each lead in turn and with the engine running at various different speeds saw no break in the light regularity. I believe I have given an account of how I checked the timing and found the line to remain steady. The engine shows no sign of missing until out on the road; particularly under load. Then it seems to die and backfire; go along a bit then die and backfire again. Sorry, I don't know what an "inductive" timing light is. My light is connected directly to the lead and has never given trouble. Also, how do you check plug wires under load? I am working alone, so no help here.

If I place the palm of my hand near to the exhaust exit I can feel regular pulses of pressure but occasionally there is a cough.

Ray.

Ray, An inductive pickup light has a clamp on lead that attaches around the wire and picks up the spark pulse which triggers the strobe. Light springed jaw clamp. You can move it from plug wire to wire with engine running and no risk of shock. That would make it handier testing on the road, just clamp on one wire and switch the strobe on or tape down trigger depending on light setup. Attach the light to the body with bungee or tape so it points toward you and drive. If no irregularity, you can stop and switch to another wire while engine still running. Or you can start out with it clamped on the main coil wire to distrubutor first to see if you lose spark to all at once, The former would isolate a single wire, the latter would point to coil or some other problem on primary side of system.

The way you describe it "die and backfire, die and backfire" sounds more like losing spark to all. I can duplicate that by turning off the key 2-3 seconds and switching back on, hard on the muffler! That occassional "cough" you feel, isn't that in itself a missfire? But still, at idle it could be mixture instead of spark.

Now, if you understand my point, I will leave you alone. Cheers! Talleyho! Pip-Pip and all that rot!

[TexasJohn55]

Ray, I have been pondering your problem. You said that you removed the electric fuel pump and hooked up original vacuum delivery system. Did you have that problem before doing this? You also said one mechanic wanted to hook up the electric to test out problem. In post 31 you conceded that fuel starvation might be a possibility. If the engine is under load at higher rpms that would drop the intake vacuum and possibly compromise fuel delivery, but I must confess I know nothing about that system. Is it too difficult to hook up the electric pump?

Have all your parts arrived and been installed for the ignition system?

Didn't know if you had anything to update us on. John

[R.White]

Hello John. I appreciate your taking an interest. I think we are thinking along the same lines.

When I got the car it was a non runner and hadn't run for several years but it did have the electric fuel pump supplying fuel to the vacuum tank. The tank was decrepit and not working as such but with the fittings blocked off had served as a means of supplying a gravity feed to the up draught carb. When I got the car running I noticed the vac tank was leaking so I restored it. (see my thread). As the previous set up was quite dangerous and non original I removed the electric pump and returned the system to original. I have a suspicion that there is presently insufficient vacuum to keep the carb supplied after the car has been running on the road for while. Just as you suggest. This may be causing a lean mixture and subsequent backfire/ drop off in power. Perhaps there is a vacuum leak somewhere; although I have tightened the fittings and applied thread seal. Another possibility is a partial blockage in the fuel line. My suspicions were deepened when the other day I fitted my spare carb (following some refurbishment) to see if there was an improvement. The empty vacuum tank would not fill with fuel. There was insufficient vacuum so I had to prime the vacuum tank by pressurising the main tank. Once primed, the carb float chamber filled and the car started. Despite originally checking for pressure leaks perhaps a valve in the top has begun leaking?

I have bought a new 'SU' 6 volt low pressure petrol pump (AUA26) and will fit it to see if the vac tank theory stands up. (The original pump is broken). At the moment, I am unsure whether to send a fuel line direct to the carb and see if it floods or not -due to too much pressure - in which case I will need a pressure regulator of some kind. I expect a clamp on a flexible pipe or a smaller bore pipe will suffice temporarily. The other option is to blank off the vacuum fitting at the manifold and attach the pumped supply (1.5 lb psi) to the vacuum tank and rely on it's float and valve to cut off the pump and ensure gravity feed to the carb.

The ignition parts have arrived at last. Yesterday I fitted the new cap, rotor arm, leads and new plugs for good measure. The results were disappointing. The engine was misfiring all over the place. I quickly traced the problem to the new cap which is a sloppy fit in the distributor and moving about with the rotor arm. Also, the numbers on the cap do not correspond to the plug leads. It must be the wrong cap.

To add insult to injury the starter motor (which took 6 months and cost cost me £500 to have rebuilt) is smoking and trying to burn itself out.

Sometimes you just can't win.

Ray.

Edited June 17, 2013 by R.White (see edit history)

[MikeC5]

Yikes, sorry to hear that things are not going well with the D.B. Ray. Do you have one of those Might-Vac hand vacuum pumps? They can be handy in trying to diagnose vacuum leak problems. You can disconnect the fuel line from the tank, block it off with a pipe thread plug or some other substance (wax, modeling clay) and then apply vacuum to the vacuum inlet port on vacuum tank (disconnect from engine). After several pumps you should be able to build up 10 inches or so Hg (different unit over there I suspect). If it fails this test, disconnect fuel line and plug fuel inlet to vacuum tank and try again. If you can build vacuum then the fuel line itself may have a pin hole or bad connection. You can even test the line itself this way. 1/4 inch copper tubing isn't isn't too terribly expensive and is easy to bend. The vacuum pump tool with misc rubber fittings/hoses sells here for around $50 for plastic ones (Mityvac Vacuum Pump - Save on Mityvac Pumps at Harbor Freight!). I use it to bleed brakes and clutches too.

[Guest occrj]

Hi Ray,

I use an electric 6v SU pump on the truck. I remember when I first ran up the engine years ago, with a 12v supply and 12v SU pump rigged up temporarily, it'd flood its Stromberg carb. When I altered my current setup recently, plumbing the new 6v pump direct to the carb, there were no flooding issues. It didn't affect the running problems that I've had with the truck, but there was no flooding. I think I'd be inclined to install the SU pump if there are no flooding issues, bypassing the vacuum tank entirely, to see if that cures the running woes you've had. If it does, then there's something up with the tank or its plumbing. If it still plays up, maybe use a tin of petrol in the passenger footwell and run off that, again to see if it makes any difference.

RJ

[Guest DodgeKCL]

Yikes!! A $1000 to have a starter rebuilt!! But then highway robbery was invented in England.

[Guest 1930]

I thought it was Australia, no wait thats where they were sent for vacationing

[R.White]

Too true. The guy had done a first rate job in restoring a voltage regulator/cut-out for my Austin so I had no hesitation in entrusting the North East starter motor to him. Big mistake.

I think he goes by the name Turpin The mask and pistols should have given me a clue. :eek:

Ray.

[R.White]

I thought it was Australia, no wait thats where they were sent for vacationing

That the Antipodes was the only transportation destination for British convicts is something of a sophism. There was a time when convicts were transported to colonies in America until the British were ejected following independence.

[Ron Lawson]

Ray Been away working I will check when I am next able to Looks like you need a manifold too

[R.White]

Thanks Ron. I could use a manifold but then I have a problem with the coupling. Mine has had a 3 point flange welded to accept a modern exhaust. I doubt contemporary exhaust pipes and fittings can be found to fit...... but I may be wrong?

Also wanted: 6 volt starter and water pump.

Ray.

[Guest 1930]

That the Antipodes was the only transportation destination for British convicts is something of a sophism. There was a time when convicts were transported to colonies in America until the British were ejected following independence.

Those guys must have been our first governing officials

[R.White]

That would explain a lot!