could all these probs be fuel pump related???

[wnarunm]

I just purchased an '87 We4 and am very excited to take it to the track and try her out..... Of course I must iron out all the bugs with it and get it running right...........

Here are the symptoms......
- The car takes a more than a few cranks to start, particularly if it has set.
- The idle vac is 15* in park and 12* in drive
- It reaches 15 psi boost and starts to buck and feels like it falls on its face (I get out of it!)
- My knock gauge only sometimes gets into the orange.... most of the time still in green (its a caspers)

Here is what I know....
- It has a walbro 340 pump
- an accufab adjustble regulator
- I installed a fuel pressure gauge today and with the key on it would prime to 40* and then IMEADIATLY fall back to zero.... When i went to crank it, the gauge had to build pressure and as soon as it hit 30* it cranked. the pressure read 50* with the line off... I adjusted it too 42* and took her for a spin. idling around it was 35* and when it reached 0 psi boost it had reached 42* and anything after that it started dropping and when it began missing and sputering in the top end it had fallen to 30*
- and lastly as soon as the engine is shut off the gauge drops completely to zero in like half a second.


My question is.... what could all this be? and what holds the pressure in the system when the engine is shut off? Obviously this woul dmake my car very lean and could cause the bucking. It had a full tank of 93 octane when i did this.

Thanks so much!!

 

[wnarunm]

stock turbo and injectors btw.

 

[rob nolan]

To me it sounds like a leaky injector.

 

[wnarunm]

a leaky injector wouldnt cause the fuel pressure to drop 20 numbers under boost conditions would it??? Maybe my regulator is bad?

 

[wnarunm]

I just checked and there is no checkvavle in the system at all. Im guessing the previous owner removed for track duty?

 

[pacecarta]

aside from a leaking fuel line your fuel pressure has three ways to drop , injector leakage(you would most likely see a big puff of smoke on startup when the cylinder(s) fires) .fuel regulator ,and the check valve in fuel pump
more than likely its your regulator and its the easiest to change out as a first step

 

[scottyb]

I wouldn't trust that fuel pressure regulator.
I ditched my Accufab after one day, but others love them.
Your drop in pressure is likely either a bad FPR or bad pump/check valve. You can rule out the FPR easily. Go get a 237 regulator at the junkyard for 10 clams. They were on all the 3800 series 1 engines, and make ~ 45lbs line off.

If it runs good, then it's a bad FPR, if still bad, then most likely the pump.

I don't think a leaky injector would cause your symptoms, especially an instant drop from 40+ lbs.

 

[pacecarta]

just went back to the service manual and i missed one .
normally not a problem with the stock pulsator that connects fuel pump but with the 340 its replaced with a short rubber fuel line usually held with two clamps , that short fuel line from the fuel pump in the tank could be leaking

 

[scottyb]

Originally posted by pacecarta
just went back to the service manual and i missed one .
normally not a problem with the stock pusator but with the 340 theres a short rubber fuel line from pump usually held with two clamps , that short fuel line from the fuel pump in the tank could be leaking

Read about that one before, too.

 

[NM Tom]

Had the EXACT same problem and it was the small hose that replaced the pulsator. Car would hold 43 # pressure when not under boost. As soon as boost would come on the pressure would drop. The hose had split and was just releasing the fuel back into the tank. Good luck!

 

[wnarunm]

FIXED IT!

I took apart the accufab regulator today and it had two little pieces of metal and one of which was the size of an eyelash (looked like a piece of thread) and was holding the regulator open at the seal to the bypass. Well, cleaned it and put it back together and now im seeing 58* at wot! And it cranks really easy now that the pressure dont drain down, it holds 40* for like an hour!

Thanks for eveyones input....