86Pacecar

1986 Convertible
I've had a difficult cold start problem for quite some time and it always takes alot of cranking time and multiple tries to get it to fire. Since this is not a daily driver I've just let the problem go until now.
So last weekend I went to use the car and it would not fire off, a few times it almost fired but would not get going. Did the a quick check and it had spark so it led me to believe a fuel problem. I did not have a pressure guage handy but I checked the schrader valve and there was fuel at the rail. No pressure when I depressed the valve, just a bit of fuel coming out. So I grabbed a can of starting fluid and put a quick squirt into the plenum (I know its bad but it was a quick way to check). Car fired up and ran but with a bit of a rough idle that has been happening for a while as well. Shut off the car and it would fire right up. I'm suspecting fuel pressure, checked the FPR for gas in the line as it's an easy obersvation and it was good. Listened for the fuel pump to prime but it was very faint and made some clicking noise. Too loud by the exhaust to hear while rumnning.
Yesterday I got a pressure guage hooked up and tried to start the car again, zero PSI when I hooked up. Pump primed up to 10 PSI and stayed there, anther turn of the key to prime again and it increased to 20 PSI. More attemps to prime and it would not go above 20 pounds, however it would not leak down, just stayed at 20. So before I replace the fuel pump I decided to put in a new fuel filter. Old one was full of junk and was plugged pretty good so I'm thinking that I might get lucky and thats the issue. No go, same 20 PSI after a couple of key turns to prime. Once agan I shoot a squirt of starting fluid and the car fire right up and the fuel pressure gets to about 37 PSI and runs. Shut off the car and the pressure drops a bit to about 32 and stays there for at least a half hour. Turn the key and the car starts fine as I would expect with decent fuel pressure. To test the FPR I removed the vac line with the car running and the PSI increased to about 40 and the car idled a bit smoother but dropped to 37 PSI when reconnected.
Do I have a weak fuel pump? My guess is the pump gets constant power when the car is running and it generates enough pressure to keep the car running but it needs time to do it. After work I may try to jumper the pump with constant 12V to see if it will build pressure that way. Anybody ever have a weak pump that slowly died like this?

bjankuski

It sounds like you might have a leak at the pulsator that is attached to the pump or the pump itself is bad. You could try clamping the return line after the regulator to see if the pressure jumps up, but since you mentioned that the fuel pressure holds at whatever pressure the pump get it too so the regulator does not seem like the problem.

Keith Huffstutler

How does the pressure hold up over night? I wouldn't ignore the FPR as the cause (or part of the cause).

86Pacecar

I rarely drive the car so most times it's a week between driving so the hard starting isuue happens everytime. I'm guessing it's down to zero after a week. I wiil check this afternoon after work as it will be almost a day since it was running.
Even starting the cycle with zero pressure I would think that the 2 seconds of pump running (assuming good pump) should get it past 10 PSI.

aklim

Cold Start Injector?

86Pacecar

Its been removed and chip updated to compensate

L.V. Vette

Though my 91's symptoms were a bit different, I just went thru a fuel pressure issue. Mine would prime to 42 then drop to 20 immediately and stay there. I too checked the FPR's line and it did not have any evidence of fuel. Yet, that is what it turned out to be. Replace regulator and now my pressure stays at 42.

aklim

Sounds like fuel so how are the injectors?

86Pacecar

Seems my problem is opposite of yours. I cannot get to 42 PSI until the car is running then to 40 with the FPR disconnected. Hook the FPR back up and it drops to 37-38 which is expected from a functioning FPR.
Anyway hooked up the guage this afternoon and primed the pressure to 20 after 2 turns of the key. Jumpered 12V to terminal G to activate the pump and it slowly built to just over 30 and would not go higher. I was able to get it started after a few times of it catching but not firing. the pressure would drop while cranking and once it fired up it climbed to 40 with the FPR off. It's been about 3 hours and my pressure has dropped to about 20 PSI and the pump when primed cannot go higher.
I think I will jumper 12V constant when I try turn it over to see if it maintains pressure that way.

i've had the car about 14 years and I've never touched the pump so it would not hurt to replace it.

aklim

Unless your year is different, for me, first turn gets a prime. 2nd one in quick succession gets nothing.

Get THIS. Everything you need to do the job.

L.V. Vette

Agreed. Wish I had used this kit. May as well eliminate the pulsator, another unnecessary place for potential fuel pressure leak

aklim

http://www.racetronix.biz/itemdesc.asp?ic=PIK-006&eq=&Tp=

vader86

Pinch off the return line to see whether the FPR is having an issue, but I believe your pump is dying.

aklim

Sounded like he did the pump already when he said

OP Please confirm

86Pacecar

I have not replaced the pump yet, that was a different poster. I plan to ge to it this weekend and will post back the results.

86Pacecar

Put a new pump in and still have a slow to pressurize issue. It will pump up a bit faster now but still takes about 5 seconds to pump up to 40 PSI. I guess the next step is the regulator.

aklim

Check power.

86Pacecar

Pump is running and the car does start much faster as it pressurizes in half the time of the old pump. to watch the guage it just slowly rises from zero to 40, not almost instantaneous that it's supposed to be.

I will check to verify I have a solid 12 volts to the pump.

Hot Rod Roy

If you had a bad pulsator, the pressure would drop as soon as you shut off the ignition, which is not the case. It sounds to me like you have a plugged up fuel line. Try removing your fuel filter again. Can you blow thru it?

You are right. Your fuel pressure should rise rapidly when you turn on the ignition. Look into your fuel tank. Does the bottom of the tank look clean?

aklim

Mine jumps up instantly. If you can see the gauge rise up slowly within the 2 seconds, you have another issue. I'm not sure what there is north of the filter that can do this. Did you crimp off the return line yet and see if it rises faster?