Stock Fuel Pump - Pressure too high
04-04-2014, 08:38 PM
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Stock Fuel Pump - Pressure too high My situation is in a custom application...I am building a 1938 Plymouth street rod and using the drivetrain (and related items) from a 2000 Trans Am, which had 45k miles. I wanted to keep the motor and fuel system completely stock for reliability, troubleshooting, etc. I have the original fuel tank and pump module from the donor car, and an additional fuel pump module. I believe both modules are factory GM, but do not know how to verify for certain. I used the factory lines and fittings, but shortened a line to fit. Also using the stock 'T' bypass to return fuel to the tank. The filter is brand new. Had the injectors cleaned and rebuilt, and flushed the fuel rail. The motor starts and runs fine, but clearly smells rich. I am monitoring vitals using OBD software, verified motor warmed up to 190-195 degrees, and using brand new O2 sensors. Fuel pressure was 70 psi with original module, 65 psi with second module.
Troubleshooting so far… I followed the GM diagnostic checklist for the rich condition, testing for obstructions in the lines, return, etc…using the second module. Results pointed to faulty regulator, so I purchased a new regulator and installed. Fuel pressure was still 65 lbs. Swapped regulator to original module, reading went from 70 to 65, noticeable improvement but still did not solve problem. Tested with three different mechanical gauges, fuel pressure reading is still 65 lbs with either module, whether motor is running or not. I do not have the tank pressure sensor wiring connected to the PCM, because I have not converted the filler neck to use a modern style pressure cap, but the emissions system is disabled in the PCM. I have tried both sealing off the filler neck and venting the neck wide open…no difference.
Does anyone have any suggestions on what else to check?
Troubleshooting so far… I followed the GM diagnostic checklist for the rich condition, testing for obstructions in the lines, return, etc…using the second module. Results pointed to faulty regulator, so I purchased a new regulator and installed. Fuel pressure was still 65 lbs. Swapped regulator to original module, reading went from 70 to 65, noticeable improvement but still did not solve problem. Tested with three different mechanical gauges, fuel pressure reading is still 65 lbs with either module, whether motor is running or not. I do not have the tank pressure sensor wiring connected to the PCM, because I have not converted the filler neck to use a modern style pressure cap, but the emissions system is disabled in the PCM. I have tried both sealing off the filler neck and venting the neck wide open…no difference.
Does anyone have any suggestions on what else to check?
Last edited by 38 Streetrod; 04-04-2014 at 10:32 PM.
04-04-2014, 09:45 PM
#2
Ok so your only actual problem is the exhaust smells rich ???
No actually drive ability problems ...??
No check engine .....what's the fuel trim %%. What's the coolant temp sensor reading ??
Any mods ?? Stock exhaust ??
Any chance your just chasing your tail and theirs actually nothing wrong with it ??
No actually drive ability problems ...??
No check engine .....what's the fuel trim %%. What's the coolant temp sensor reading ??
Any mods ?? Stock exhaust ??
Any chance your just chasing your tail and theirs actually nothing wrong with it ??
04-04-2014, 10:23 PM
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Yes…car is not driveable yet, still under construction. No check engine light, stock fuel trims, coolant 190-195 degrees. Stock exhaust manifolds, true duals, 2.5 pipes/mufflers, no cats, rear 02s disabled.
Smell is strong and 65 psi seemed high. I just wanted to correct any fuel system/plumbing problems while they are still easy to access.
Smell is strong and 65 psi seemed high. I just wanted to correct any fuel system/plumbing problems while they are still easy to access.
