Fuel Pressure Reading - Help

[Guest Corvanti]

after searching threads and looking thru the service manual, i can't seem to find the correct or average fuel pressure readings...

with key on: 10psi and drops down.

at idle (or any rpm up to 3500): 23psi.

seems i recall reading that it should be over 40psi at idle, but may be thinking of another vehicle (old age ).

would appreciate a little help, thanks!!!

[Ronnie]

I think 40 is about what it should be. 23 psi is too low. It is an electric pump. Engine rpm should not change the pressure. Pressure is controlled by the fuel pressure regulator that returns fuel to the tank when proper pressure has been reached. You could have a faulty pressure regulator or a bad fuel pump. Remove the vacuum line from the regulator and see if there is any gas in it. If so I would change the regulator first. I assume you have replaced the fuel filter on a regular basis?

[Guest Corvanti]

i purchased the reatta 4 weeks ago.

the pressure regulator vacuum is clean and dry. it looks fairly new - its a Bosch.

i picked up a new fuel filter, will replace that and hope that helps. not looking forward to fuel pump replacement if it comes to that.

still waiting for the new balancer, crank sensor, and oil pressure sensor to arrive (in my "stumbling problem thread"), so, it looks like i'll be busy for awhile!!!

[Ronnie]

While you have the filter off... Do you have the proper fittings to connect the fuel pressure gauge directly to the line coming from the pump to the filter? If you could do that you could tell if the low pressure is caused by a bad pump or if the regulator is your problem. You can apply 12 volts the fuel pump prime connector to momentarily run the pump to test the pressure. Always be careful when making fuel line connections to prevent leaks when working with gasoline under pressure.

Fuel Pump Prime/Test Connector Location*-*ReattaOwner.com

[Guest Mc_Reatta]

Fuel pressure specifications and tests are in Chart A-7 on pages 6E3-A-30 and 31.

Your pressure is way low and the fact it doesn't hold when pump stops looks like a faulty pump.

Might want to hold off on all your other electrical projects as this is why your car doesn't want to start or run.

[Guest Corvanti]

thanks guys for the help!!!

the fuel filter and its connections are quite corroded. i sprayed some P.B. Blaster on both and managed to loosen the "bottom" connection. the "top" connection won't budge, so i gave it a p.b.b "bath" and will probably wait til tomorrow to try it again.

i'm hoping that the low pressure is due to a fuel filter that appears not to have been replaced in the last decade. but with my luck, it will probably be the pump.

i think i have a fitting (somewhere) that will work on the "bottom" fuel line to connect the pressure pump.

and thanks for the location in the manual for the "fuel system pressure test"!!!

when i purchased the reatta 4 weeks ago, all it seemed to need was the right headlight crank assembly - purchased from a vendor here and installed - no problems, and center armrest - same as above, and repair the driver's side power window - that's now on the back burner. it ran great for a week - the first time i took it farther than 10 miles away, it took its first "dump", and more problems keep popping up!!! :mad:

oh well... i still like it!

[padgett]

Just a word of encouragement: fuel pumps usually either work or don't, low pressure is possible but not common. Should have 38-40 psi on the rail at idle. What happens when revved - goes up or down or stays the same ?

Key on just runs for about 2 seconds. If then drops could be a leaky regulator or injector (if the latter would be black smoke/stumble on start. Since not mentioned I'd look for a leaky regulator (have to remove to check).

[Guest Corvanti]

padgett: fuel pressure was 23psi from idle to 3500rpm.

the fuel pump is working, but wouldn't a clogged pump or inlet filter lower the psi coming out?

i've really had a bad day with the inline filter. after a day of soak with p.b. blaster on the top connection it still won't budge. i didn't find anything on hand to connect the pressure tester to the line from the fuel pump. i tried some f.i. hose and clamps, etc. but couldn't get a reading. i jumped a 12v wire to the green connector as instructed, and could hear the pump running, and the rubber hoses and clamps leaked fuel, so....

i'm about to put vice grips on the top connection and a breaker bar on the bottom "nut". i suspect that would just tear the old filter into pieces.

i've never spent more than 15-20 minutes replacing a fuel filter, even on relative's fuel inj. vehicles.

as slim pickens said in "Blazing Saddles": i am depressed!!!

[padgett]

Would think with a clogged filter that the pressure would drop at the rail as demand (revs) goes up. This sounds more downstream like the regulator.

[Guest Corvanti]

ok, after a day off to rest my titanium parts in my back, hip and knee, the fuel filter is done. i'm still getting 23psi reading at the sch. valve. only difference is with key on/engine off it's holding at 6psi.

again, the fuel pressure regulator seems to be fine as far as no gas in the vacuum line - running from idle to around 3000 rpm. anything else w/the fpr i should be looking at?

after a "normal" amount of time after fuel pressure was sufficient to start the vehicle, it stumbled and died 2 or 3 times (see my other thread). finally got it going to do the fp test... about 10 minutes later, i started it again and it stumbled again. but finally settled down and drove it around the block twice.

battery voltage was fine while driving (had a trickle charger on the battery since sunday).

the crank/harmonic balancer and oil pressure switch arrived today and i expect the crank sensor tomorrow, so i reckon i'll start preparing for that now, and revisit this after that.

sorry for the long post, but wanted to try to include as much as i could about it.

thanks!!!

[Guest Corvanti]

was finally physically able to hit the garage today got her started and did an old fashioned vacuum check - sprayed with carb cleaner. i got a "hit" on the hose that is closest to the intake manifold. the metal part goes underneath the engine on the driver's side.

i twisted the rubber hose and the fitting came out. appears that the p.o. had cut a white vacuum fitting and jammed it in there. i replaced the fitting, made sure it was secure and replaced the rubber hose - the old hose was not the 90 degree hose like the other next to it is.

it now starts on the 1st or second try. no "stumbling" after that. the fuel pressure reading is up to 18psi key on/engine off (instead of 6psi), but engine running still shows around 23psi. starting to think my new gauge (from "china" freight) is defective. may try it on my other car tomorrow to see what kind of reading i get.

i could use some guidance here, please...

i still need to replace the crank balancer and sensor, as well as the the oil pressure sensor. when i'm up to it. if my orthopedic surgeons knew what i was doing, they would not be happy docs...

[Guest Mc_Reatta]

Screw your fuel pressure onto one of your tire's Schrader valve and then compare it's reading with a tire gauge's. Think its the same threads. That will tell you if the pressure gauge is off.

I'm looking at measuring the pressure going into the fitting at the fuel filter, and again at the inlet to the fuel rail.

Need to rig an adapter convert the 1/4 in NPT female threaded adapter that is in the pressure gauge kit to a 3/8 female flare fitting to match the end of the filter and rail input. Had to buy 2 fittings at Lowes to rig. One is a 1/4 NPT male to 3/8 male flare, and the a double ended 3/8 female flare to change gender.

I'll let you know if it works for sure as soon as I can crawl under one of mine with a similar problem.

[Guest Corvanti]

the valves aren't the same, but the fuel pr test kit had another fitting that worked - the fp tester was exactly the same reading as the tire gauge...

let me know if you find the fittings to hook it up at the rear of the fuel filter.

i think i'll start on bad crank balancer, crank sensor and oil pressure sensor today, and revisit the fuel pressure problem later...

since replacing the fuel filter, she has been starting everytime on the second try. and seems to be running fine (except the balancer, etc.), but i'm not trusting yet to drive much more than walking distance from the house.