Questions for Dave W.

First I have the 350 Vortec and it is running pig rich. Need further help please.

1) How do one know if it is running in Limp Home Mode (LHM)?
2) Had 65 pph injectors, changed to 61 pph injectors, Fuel Pressure 12-14 psi still runs rich
3) Much AC noise on Knock Sensor wire. Can Knock be turned of in TunerPro. Also will try 1 Kohm resistor on wire to ground.
4) Can 74 pph 7.4L injectors be used by raising fuel pressure?
5) Is 74 pph injector tighter, then increase fuel pressure to it yields higher fuel flow?
6) If changing to 74 pph injectors, what fuel pressure as a start should be used?
7) Should I use external fuel pressure regulator referenced to manifold vacuum?

Need help. Must be missing one of the basics. Will try the 7.4L injectors and set the fuel pressure to 20 psi to see what happens. Please advise. Thanks.

You probably need 30 psi to meet the demands of you engine with the 65 lb/hr injectors. Most people use a standard regulator modified to be adjusted with the turn of a screw. Just take it easy, one step at a time.

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Originally Posted by DOCBAWRENCHTURNER

You probably need 30 psi to meet the demands of you engine with the 65 lb/hr injectors. Most people use a standard regulator modified to be adjusted with the turn of a screw. Just take it easy, one step at a time.

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With 61 or 65 pph injectors the lowest the adjustable fuel pressure regulator can achieve is 12-14 psi. With this combination the 350 Vortec is running PIG RICH Wide Band AFR says 10.x:1 at idle. Best guess, suspect the wrong Memcal being used. Will use the one in the 1995 Chev 5.7L C1500 pickup that has 16197427 ECU. Once this situation is fixed, then use '94-'95 7.4L 30 psi injectors. Will adjust the fuel pressure regulator to approx 20-30 psi and see which setting gets somewhat close to better AFR. Then fine tune from that point.

1) How do one know if it is running in Limp Home Mode (LHM)? ~ Not sure, I've never experienced LHM. It's my understanding the engine will run very rich.

2) Had 65 pph injectors, changed to 61 pph injectors, Fuel Pressure 12-14 psi still runs rich ~ Maybe you running in Limp Home Mode?

3) Much AC noise on Knock Sensor wire. Can Knock be turned of in TunerPro. Also will try 1 Kohm resistor on wire to ground. ~ I think setting the parameter minimum temperature for knock retard to maximum will disable knock retard.

4) Can 74 pph 7.4L injectors be used by raising fuel pressure? Raising fuel pressure will increase an injectors PPH. Lowering fuel pressure will lower an injectors PPH.

5) Is 74 pph injector tighter, then increase fuel pressure to it yields higher fuel flow? Maybe it would be good plan to have the injectors flow tested at different fuel pressures to know what you are actually working with.

6) If changing to 74 pph injectors, what fuel pressure as a start should be used? I would use stock fuel pressure the 74 PPH injectors were intended to use.

7) Should I use external fuel pressure regulator referenced to manifold vacuum? It's a personal opinion, I would not use the vacuum referenced fuel pressure regulator.

dave w

If it was in limp mode wouldn't be data over aldl

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Originally Posted by delcowizzid

If it was in limp mode wouldn't be data over aldl

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I was about the say the same thing. Both times I have went into LHM by mistake (programmed eeprom, but forgot to put it back into the ecm :mad1: ) The engine started, ran very poorly, and I could not connect to it.

I have seen this twice once when someone smashed the fuel return line putting a new motor in and another time when someone used vice grips to pinch off the return line to replace the fuel pump and forgot to remove the vice grips. if its not a fuel supply or return issue do you have the capabilities to datalog? is your CEL (Check engine light) on? how are you checking fuel pressure?