Fuel Pressure Regulator for 7.4 Vortec
March 14th, 2017, 11:13 AM
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Fuel Pressure Regulator for 7.4 Vortec
1998 Chevrolet C3500 7.4 145,000 (seldom used) Fuel Pressure problem.
In search of a way to improve my lousy gas mileage (6 mpg), I have been watching fuel pressure. I only get 50 psi. Refs say you need minimum of 55 (specs 56-62). I replaced fuel pressure regulator with aftermarket PR217 knockoffs (Chinese) and still get only 50 psi.
Obviously my frugality is not working. So I go to local GM and they want $145, which I find robbery. So I then go to Delphi which markets FP10021 rated at 56.21 psi. They also market FP10075 rated at 61.8 psi.
Finally able to find the Delphi customer help site (difficult to find). A bit intimidating as Delphi sells lots of different stuff so you have to guess which division covers your part. I sent query to Fuel Systems and got nice reply that FP10021 was the right one. It is currently on order so I cannot report if that fully solves the problem.
Getting to this point, I think you may find the below interesting.
1. My first guess was that the fuel pump was not up to speed. I have a old fuel pressure test kit and one of the adapters allowed me to tap into the fuel filter outlet side. That gave me a steady reading of 80 psi. This tells me the FP is working and the check valve is okay as well.
2. The 7.4 vortec fuel pump regulator is impossible to see, moreless get to the vacuum line to test the regulator by pulling the line. You should see an increase in pressure. I was unable to do that. Perhaps by aiming the vacuum tube of the FPR upward during install maybe it might be reachable, but you then run the risk of crimping the vaccum line.
3. My next concern was the possibility of leaking fuel injectors. To check that you need to pull the upper plenum and the fuel rail and to see the bottoms of the injectors. Well before I got to that my engine came down with a hard start condition when warm. You have to kick the accelerator to the floor (flood clear). Then it would start but leave a massive white smoke cloud. Then run okay. Checking fuel pressure it would go to 50 psi and then immediately drop to zero.
Since I have the FPR on order, I decided to also change the injectors which I guess are the original Rochester which I understand are prone to leaking. Hopefully my frugality does not bite me again as I opted for a set of Bosch off Ebay for $111. A new set is like $600+ and aftermarket new is close to that. Love my truck, but my wallet more.
Anyway story to be continued.
In search of a way to improve my lousy gas mileage (6 mpg), I have been watching fuel pressure. I only get 50 psi. Refs say you need minimum of 55 (specs 56-62). I replaced fuel pressure regulator with aftermarket PR217 knockoffs (Chinese) and still get only 50 psi.
Obviously my frugality is not working. So I go to local GM and they want $145, which I find robbery. So I then go to Delphi which markets FP10021 rated at 56.21 psi. They also market FP10075 rated at 61.8 psi.
Finally able to find the Delphi customer help site (difficult to find). A bit intimidating as Delphi sells lots of different stuff so you have to guess which division covers your part. I sent query to Fuel Systems and got nice reply that FP10021 was the right one. It is currently on order so I cannot report if that fully solves the problem.
Getting to this point, I think you may find the below interesting.
1. My first guess was that the fuel pump was not up to speed. I have a old fuel pressure test kit and one of the adapters allowed me to tap into the fuel filter outlet side. That gave me a steady reading of 80 psi. This tells me the FP is working and the check valve is okay as well.
2. The 7.4 vortec fuel pump regulator is impossible to see, moreless get to the vacuum line to test the regulator by pulling the line. You should see an increase in pressure. I was unable to do that. Perhaps by aiming the vacuum tube of the FPR upward during install maybe it might be reachable, but you then run the risk of crimping the vaccum line.
3. My next concern was the possibility of leaking fuel injectors. To check that you need to pull the upper plenum and the fuel rail and to see the bottoms of the injectors. Well before I got to that my engine came down with a hard start condition when warm. You have to kick the accelerator to the floor (flood clear). Then it would start but leave a massive white smoke cloud. Then run okay. Checking fuel pressure it would go to 50 psi and then immediately drop to zero.
Since I have the FPR on order, I decided to also change the injectors which I guess are the original Rochester which I understand are prone to leaking. Hopefully my frugality does not bite me again as I opted for a set of Bosch off Ebay for $111. A new set is like $600+ and aftermarket new is close to that. Love my truck, but my wallet more.
Anyway story to be continued.
Last edited by Russ B; March 14th, 2017 at 11:54 AM. Reason: Additional info
March 14th, 2017, 1:50 PM
#2
why not just check the fuel trim readings. If the fuel trim is not adding over 10% the system is not fuel starved. If you were fuel trim lean dtc would be setting.
another test would be to disconnect the vacuum source to the fpr and do a wot. if the fuel pressure does not drop more than 3psi..the pump is good.
your not having drivability issues correct? don't fix what ain't broke.
before i buy anything, I would make sure your fuel pressure gauge is accurate.
another test would be to disconnect the vacuum source to the fpr and do a wot. if the fuel pressure does not drop more than 3psi..the pump is good.
your not having drivability issues correct? don't fix what ain't broke.
before i buy anything, I would make sure your fuel pressure gauge is accurate.