JMO413 Posted September 28, 2018 Posted September 28, 2018 Just put everything back together my fuel pump wouldn't stop running. Fuel pump shuts off now but I have a new issue. With the engine running or shut off the ECM shows all the settings are jumping around. This is with a snap on scanner hooked up. There scanner shows rpm jumps between 750 and 3000 rpm and the tach stays steady at about 1000. Not sure what happened. All the sensors reading like they are jumping around. It runs okay. Not sure what happened?
Ωhm Posted September 28, 2018 Posted September 28, 2018 You mentioned before you had two PCM's (88&89). Did the scanner work OK before on both of them?
JMO413 Posted September 28, 2018 Author Posted September 28, 2018 Yes it worked correctly on both. I have done the ground refresh and the sensor ground refresh. The readings on the scanner jump around with it running or just key in running position. The engine stays at idle and idles nicely. It drives fine under 2500 rpm then it's like there's no input.
Ωhm Posted September 28, 2018 Posted September 28, 2018 Scanner only uses serial data from the microprocessor. If vehicle runs and operates OK, I don't know what to say. Not much help here.
JMO413 Posted September 28, 2018 Author Posted September 28, 2018 It idles well but doesn't drive well over 2000 rpm. I'm going to try the old ECM tomorrow I guess and see what happens.
cruiser54 Posted September 28, 2018 Posted September 28, 2018 Got all the ground wires attached at the engine dipstick tube stud? Clean and shiny? Done tip 5 lately?
JMO413 Posted September 28, 2018 Author Posted September 28, 2018 All grounds at the dipstick are shiny and oxgaurd applied and tip 6 is done. I have done tips 1-6,8,9,11,18,19,22, 25,29,31,& 37. This has all been done in the last two months or so that I have owned the truck.
cruiser54 Posted September 29, 2018 Posted September 29, 2018 23 hours ago, JMO413 said: All grounds at the dipstick are shiny and oxgaurd applied and tip 6 is done. I have done tips 1-6,8,9,11,18,19,22, 25,29,31,& 37. This has all been done in the last two months or so that I have owned the truck. Okay. Good job.
JMO413 Posted September 29, 2018 Author Posted September 29, 2018 Your website and tips are amazing. Thank you. Still working on it a little each day.
JMO413 Posted September 29, 2018 Author Posted September 29, 2018 So I had a little time today. Pulled the ECM out to put in the old one. The real trip is that the scanner fluctuates the same way without a ECM attached to the truck. With the old ECM installed the scanner reads the same way. The truck idles well but that's about it. Not sure where to go now?
Ωhm Posted September 30, 2018 Posted September 30, 2018 Scanner and maybe the ECM seem to be floating (no ground). Check for continuity between Diagnostic Connectors and the battery negative. D1-3 (G105) and B- D2-7 (G104) and B- Has this vehicle ever run properly?
JMO413 Posted September 30, 2018 Author Posted September 30, 2018 I pulled the disc out of the scanner and now it reads right. It still doesn't run quite right. It hesitates when you push on the accelerator. Going to get a fuel pressure gauge tomorrow to check the fuel pressure again. Yes it ran great right before the fuel pump kept running.
JMO413 Posted September 30, 2018 Author Posted September 30, 2018 The fuel pump is the only thing the PO had touched that I haven't redone yet. That is about to change I have a whole 18 Psi work the fuel pressure regulator hooked up or not still the same. It will kick up to 20 if you bypass the ballast resistor. Check the injectors with a stehoscope and they are all pulsing. He used old cracked fuel line at the filter. Hopefully the same issue in the tank. The fuel pressure also drops as soon as you shut it off. I mean straight to 0.
JMO413 Posted September 30, 2018 Author Posted September 30, 2018 Before I pulled the fuel pump I checked pressure at the fuel filter. It's over 40 psi. I guess I need a new pressure regulator.
Ωhm Posted September 30, 2018 Posted September 30, 2018 If you "T" in between the fuel filter and fuel pump with 40+psi on the gauge, while only reading 18-20 psi under the hood at the schrader valve, maybe your dropping pressure across the fuel filter.
JMO413 Posted September 30, 2018 Author Posted September 30, 2018 I will check but it is a week old Wix filter.
JMO413 Posted September 30, 2018 Author Posted September 30, 2018 Well someone has been at the fuel pressure regulator before. It came out with two orings on it!
JMO413 Posted September 30, 2018 Author Posted September 30, 2018 Just trying to get an extra opinion but doesn't the fuel pressure regulator make more sense. The fuel pressure drops to 0 as soon as you shut it off. And it drops to zero after it primes. Also the fuel pump held pressure when I tested it at the pump.
Ωhm Posted October 1, 2018 Posted October 1, 2018 20 minutes ago, JMO413 said: Also the fuel pump held pressure when I tested it at the pump. How did you check pressure at fuel pump? A check valve in the fuel pump outlet maintains and holds system pressure along with the fuel pump regulator.
HOrnbrod Posted October 1, 2018 Posted October 1, 2018 Try this . Easy to do and see what happens to fuel pressure and your other fuel delivery symptoms.
JMO413 Posted October 1, 2018 Author Posted October 1, 2018 I plumbed the gauge in at the fuel filter. I will get a check valve also. That makes sense. I ordered a regulator it will be here tomorrow. Hopefully I can get time after work to install it.
JMO413 Posted October 2, 2018 Author Posted October 2, 2018 So new fuel pressure fixed the problem. It has 31 PSI with the vacuum line connected and just shy of 40 with the vacuum line disconnected. She finally runs right. I am actually kind of impressed with the way it runs. The newer ECM and 4 hole injectors finally work as designed. Thanks everyone for the help work this.
HOrnbrod Posted October 2, 2018 Posted October 2, 2018 How long does it hold pressure at the fuel rail Schrader valve after you shut it down?
JMO413 Posted October 2, 2018 Author Posted October 2, 2018 20 minutes was all the longer I watched it.
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