Help diagnosing fuel system problem? 88 5.0 EFI

Andyb · 06-15-2001, 02:30 PM

Okay guys I have gone through hell with my car.

About 8 months ago I spent a lot of money for two hi-flow cats, and now they are ruined. I was visitting the muffler shop and they informed me the cats were ruined. They said rich conditions had killed the cats. So I am thinking I have a fuel delivery problem.

When I first got my car it was in absolute ghetto condition. I did a tune up on it, new spark plugs, spark plug wires, cap/rotor. Since then I have also replaced the TPS, Ignition Coil, Ignition Module, EGR Valve, 2 Hi-flow cats. I have cleaned out throttle body/idle air bypass valve.

I hooked my code scanner up and I don't remember the code number offhand but I do remember the description of the code. It said my o2 sensors were reporting the car was running rich. Well about 8 months ago the o2 sensors were replaced along with the cats.

My car also pings under hard acceleration. The timing is set to 10*. I also can smell gas fumes if I park my car in the garage. I'm no expert and that's why I am here asking, what else could be going wrong? I'm starting to think maybe I have a fuel delivery problem. How should I go about approaching this problem? I have no checked the plugs yet to see what kind of shape they are in...

Thanks,
Andy

Capri306 · 06-15-2001, 02:53 PM

Check the fuel pressure regulator for proper operation with a pressure tester. The only other thing I can think of is a clogged injector (stuck open), which can also be tested with the pressure tester. If you notice the pressure drops to zero quickly after shutdown, that would indicate a leak somewhere in the system. This would explain the gas odor. Hope this helps.

------------------
Capri306, Moderator, The Mustang Works Online
1979 Mercury Capri, 5.0L -- C4 -- 2.73
1987 Mustang LX Notch

jimberg · 06-15-2001, 03:10 PM

Make sure that there is a vacuum line going to the fuel pressure regulator from the back of the intake. If this is not there, relative fuel pressure will be high at idle and lower rpms causing it to run rich.

If that checks out, get yourself a fuel pressure gauge and make sure that fuel pressure is from 37-40 psi with the engine off. Run the fuel pump and monitor the pressure. You can run the pump by grounding the fuel pump test lead with the ignition in the on position. If you look at the test connector, it's got female plugs on either end and four grouped in a square in the middle. The single connector closest to the group in the middle is the fuel pump test lead. I just made a long wire with a male spade connector on the end that I just stick in there and ground it to the engine when I need to run the pump.

If the pressure doesn't hold steady, replace the FPR.

Considering the condition of the car that you described, I'd check the harmonic balancer and make sure nothing is sticking out. It's possible for the outer ring to slip causing the timing to be off. If you don't see anything obvious, you may want to set your #1 cyl at TDC and confirm that the timing mark matches.

Confirm that the injectors go with the MAF sensor. Maybe the idiot before you tried "boosting performance" by adding 30# injectors. That's way outside of the computer's ability to compensate. Since your O2 sensors were reporting rich and generated a code, it's a good bet that they were working fine. I don't think the computer will report a rich or lean condition unless it can't compensate.

Those are some ideas.

------------------
351W 89 Mustang GT Convertible

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06-15-2001, 02:30 PM	#1
Andyb Registered Member Join Date: Aug 2000 Location: Mesa Az Usa Posts: 19	Help diagnosing fuel system problem? 88 5.0 EFI Okay guys I have gone through hell with my car. About 8 months ago I spent a lot of money for two hi-flow cats, and now they are ruined. I was visitting the muffler shop and they informed me the cats were ruined. They said rich conditions had killed the cats. So I am thinking I have a fuel delivery problem. When I first got my car it was in absolute ghetto condition. I did a tune up on it, new spark plugs, spark plug wires, cap/rotor. Since then I have also replaced the TPS, Ignition Coil, Ignition Module, EGR Valve, 2 Hi-flow cats. I have cleaned out throttle body/idle air bypass valve. I hooked my code scanner up and I don't remember the code number offhand but I do remember the description of the code. It said my o2 sensors were reporting the car was running rich. Well about 8 months ago the o2 sensors were replaced along with the cats. My car also pings under hard acceleration. The timing is set to 10*. I also can smell gas fumes if I park my car in the garage. I'm no expert and that's why I am here asking, what else could be going wrong? I'm starting to think maybe I have a fuel delivery problem. How should I go about approaching this problem? I have no checked the plugs yet to see what kind of shape they are in... Thanks, Andy

06-15-2001, 02:53 PM	#2
Capri306 Moderator Join Date: Sep 1998 Location: Grand Rapids, Michigan, USA Posts: 1,001	Check the fuel pressure regulator for proper operation with a pressure tester. The only other thing I can think of is a clogged injector (stuck open), which can also be tested with the pressure tester. If you notice the pressure drops to zero quickly after shutdown, that would indicate a leak somewhere in the system. This would explain the gas odor. Hope this helps. ------------------ Capri306, Moderator, The Mustang Works Online 1979 Mercury Capri, 5.0L -- C4 -- 2.73 1987 Mustang LX Notch

06-15-2001, 03:10 PM	#3
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Make sure that there is a vacuum line going to the fuel pressure regulator from the back of the intake. If this is not there, relative fuel pressure will be high at idle and lower rpms causing it to run rich. If that checks out, get yourself a fuel pressure gauge and make sure that fuel pressure is from 37-40 psi with the engine off. Run the fuel pump and monitor the pressure. You can run the pump by grounding the fuel pump test lead with the ignition in the on position. If you look at the test connector, it's got female plugs on either end and four grouped in a square in the middle. The single connector closest to the group in the middle is the fuel pump test lead. I just made a long wire with a male spade connector on the end that I just stick in there and ground it to the engine when I need to run the pump. If the pressure doesn't hold steady, replace the FPR. Considering the condition of the car that you described, I'd check the harmonic balancer and make sure nothing is sticking out. It's possible for the outer ring to slip causing the timing to be off. If you don't see anything obvious, you may want to set your #1 cyl at TDC and confirm that the timing mark matches. Confirm that the injectors go with the MAF sensor. Maybe the idiot before you tried "boosting performance" by adding 30# injectors. That's way outside of the computer's ability to compensate. Since your O2 sensors were reporting rich and generated a code, it's a good bet that they were working fine. I don't think the computer will report a rich or lean condition unless it can't compensate. Those are some ideas. ------------------ 351W 89 Mustang GT Convertible