torchredfrc

I'm trying to run down a problem that seemed to be related to my fuel pump and/or the fuel filter. What was happening is while driving the car would hesitate then start driving fine again. Eventually this turned into the hesitation and no throttle response (start/sputter/die) and a tow home.

Once I got the car home I hooked up a fuel pressure gauge to the fuel line valve and the pressure would pump up to 50+ PSI on crank then quickly fall off (at which the car would die). I tried bleeding a bit of fuel off through the valve while the car was cranked and eventually it would stay running.

Now the car is back at it and won't stay running. So far I've replaced the fuel pump with a Lingenfelter high pressure pump and put a new fuel filter on. The car still cranks, the pressure spikes then hovers at 20 PSI at which time the car sputters and dies.

What is concerning me is that sometimes I can give the car a bit of gas and there will be a response. Other times I hear a "waft" and the car will sputter and die. I've tried unplugging the MAF to run SD in case it was bad but this didn't help at all.

I'm at a loss at this point as to what can be causing my issues. I was almost certain the fuel pump had decided to quit on me since the car has around 95k miles on it but that hasn't fixed my issue.

I'm going to pull the codes in a little bit, just got in from the garage replacing the filter so I'm gonna take a beer break before I tackle it again. Hopefully I'll be armed with some forum advice and I can run this puppy down. Sure miss driving the car.

8VETTE7

If you have verified that there are no leaks in the lines and just replaced the filter, it certainly sounds like a bad pump to me. JMHO.

torchredfrc

That was what I thought too 8VETTE7. Can't find any leaks but I've already replaced the pump and the filter.

8VETTE7

Don't have a shop manual for the earlier cars but is there an external regulator?

torchredfrc

I just looked in my shop manual and it indicates the fuel filter and pressure regulator are 1 and the same unit. The unit i removed from the car was identical to the unit I put in the car. The part I put in was a Microgard filter PN 33737 (FRAM GF336, PTC PGF336). According to the good folks at Checker, this is the correct part for my model year.

torchredfrc

Here is a link to the filter I used & the part number agrees with what the Oreilly auto parts site shows for my model year.

http://www.oreillyauto.com/site/c/de...2515&ppt=C0023

torchredfrc

Just pulled the codes:

[PCM] P0230 - Fuel Pump Relay Control Circuit (Old) (Current) (Immature)
[PCM] P1637 - Generator L-Terminal Circuit (History) (Immature)

I swapped the fuel pump replay with the horn relay. No change. Open to any and all ideas.

torchredfrc

Just triple checked fuse #13 (f/pmp; 20A) and it looks good.

The manual fuel pump controls in HPTuners - when i put the pump to "ON" and the car in accessory I should hear it hum right? I'm just confused why the car would pump up the pressure in the rail on crank but not hold pressure in the line at idle. Unless the dang pump isn't getting constant power somehow...

TraceZ

Maybe the ground for the fuel pump is corroded? Find out where it grounds out and clean up the connectors there.

torchredfrc

Hey TraceZ, thanks for the input. I double checked the grounds while changing the pump and filter.

I just came back in from jumping the relay. Car fires up, pressure comes up and holds. Looks like the PCM might not be commanding the relay closed... don't know how the heck I'm going to fix this one.

Anyone know if it's safe to drive with the relay jumped? Any tips for figuring out why the PCM wouldn't command the relay closed? I've tried both my keys and it doesn't seem to be the theft deterrent system.

TraceZ

Use a DVM to test the signal from the PCM to the relay.

Do you have a circuit diagram? If not, I can look for one tonight and post it.

torchredfrc

The diagram for the coil is on the relay. I'll probe it when I have a 2nd set of hands to help me out. Further than that - from the fuse box to the PCM I'm a little perplexed as to how to trouble shoot it.

TraceZ

I'm guessing the PCM drives the relay directly. Your car is a 99, correct?

torchredfrc

Yes to both questions.

Bill Curlee

torchredfrc

Looks pretty simple... so if i don't have 12V at the coil pins in the fuze box then I'm guessing I'll be replacing the PCM?

Bill Curlee

Examine the fuel pump circuit above. You will see that the relay has TWO power supplies. One comes from the HOT in RUN & Start and that voltage comes from the IGNITION SWITCH.

The other is relay drive power supplied by the PCM and turns on the coil to connect the SWITCH to supply high current 12 VDC to the pump. They control circuit of the relay grounds on the DRIVES side of the block and the pump and fuel sender grounds on the driver side of the frame inside the rear wheel at G-401.

MAKE SURE that your maintaining 12 VDC on the HOT in RUN & START feed. IF,,, the ignition switch contacts are BURNT,, it will NOT power the pump properly.

IF,,, the ground/s are not PRISTINE CLEAN and sound, it will NOT work properly.

Your going to need to break out a meter and start voltage monitoring and see what your losing when the car dies. Does the relay "DROP OUT" or does the pump motor stop running because it doesn't have enough current because the ignition switch is not able to provide it enough current cause of burnt contacts??????

Check out this post on IGNITION SWITCH repair:

- C5 ignition Switch repair - http://forums.corvetteforum.com/c5-t...ch-repair.html



Hope this helps!

BC

rrichar2591

Any update yet?

torchredfrc

Got stuck at work late today. Have to find a good dmm to research further. Still looking like the 12v line to the relay coil is the issue but I won't know for sure until I get a meter.

torchredfrc

Got a DMM on the 12V coil line from the PCM and it was @ 12V for a few seconds then dropped out and came back. I'm near certain this is what is causing my pump to stop running.

I'm going to start trying to figure out if the crank position sensor is working correctly. From what I understand it's the crank position sensor that the PCM uses to command the 12V off if the engine is not running (sitting in RUN and not cranked @ the ignition).