Fuel Pump Theoritical Problem

ausgezeichnet · ausgezeichnet's Garage

Is it possible for the fuel pressure to be so low that there is enough pressure on the left side (closest to the pump) for the cylinders to fire but by the time the pressure gets to the right side there is not enough fuel pressure for the right side cylinders to fire? Thanks.

RoninLB · 04-30-2005, 06:31 PM

a non experienced 3.2 guess is a big No..

unclebilly · unclebilly's Garage

The pressure would be equal everywhere - think of your fuel lines as a plenum that is pressurized by the pump.

ewave · 04-30-2005, 09:12 PM

Electrically there are only two circuits for all six injectors... The injectors for cylinders 1, 2 and 3 are wired in parallel, and for 4 , 5, 6 are in parallel. That means injectors 1, 2 and 3 all fire at the same time, and 4, 5 and 6 all fire at the same time.

I'd expect some sort of electrical problem if only half the injectors were working. Anything from a bad DME, to a broken wire or connector.

ausgezeichnet · ausgezeichnet's Garage

Ok. Thanks. That's what has me puzzled. I have the DME tested and it is OK. I used a noid to test the injectors and they are firing. I used a stehescope to listein to the injectors and they are all clicking. I used a inline spark detector and I am getting spark. Replaced the rotor, cap and plugs just ot make sure. I pulled a plug on the right side and itis dry.

AFJuvat · 05-01-2005, 07:04 AM

Sounds like the fuel pump relay or the DME relay is shot.

ALso check the ground points in the engine compartment. Make sure all electrical connetions are good and tight.

AFJuvat

Grady Clay · 05-01-2005, 07:20 AM

Mike,

Hopefully the problem is something simple in the fuel injection.

When one bank of a 911 isn’t working, one thing to check is the functioning of the cams. I would recommend a cranking compression test on all six cylinders. You might go farther and measure the valve clearance and cam timing. You are checking to verify that the 4-5-6 cam hasn’t jumped timing.

Best,
Grady

ausgezeichnet · ausgezeichnet's Garage

Ok. Thanks guys. Since the left side fires fine and actually holds a steady idle, I am focusing on something that could only impact one side. I just replaced the DME relay so I do not believe that is the problem. Although I just had a compression and leak down test last August, I will try another compression test to rule it out.

This all started about 4 months ago after removing the fan and alternator. When I removed the fan shroud I knocked off the dist cap and bent the rotor. I replaced both the cap and rotor. Since I have spark on the right side, I have focused on fuel problems. Now I am wondering if I might have done something to the distributor, which is not giving me spark at the right time. Thoughts?

RoninLB · 05-01-2005, 01:15 PM

Quote:

Originally posted by ausgezeichnet

Thoughts?

I'd follow what ewave and Grady posted for more thoughts later.

ausgezeichnet · ausgezeichnet's Garage

I checked the compression in cylinder #4. It is 179 Lbs. Last August when I last had it tested it was 175 Lbs. Lack of compression does not seem to be a problem. I had another thought, even though the injectors are firing, could the injectors still be clogged so that fuel is not getting through?

ausgezeichnet · ausgezeichnet's Garage

OK. I feel pretty stupid, but I found the problem. Of all things it was the spark plug wires not seated properly. It's running like a champ now. Can't believe it only took me 4 months to figure it out! I almost forgot how much fun it was to drive this thing! Thanks for all your help.