K1ng0011

I have swapped a '165' ECU with a TPI intake on my chevy 350. Was working fine until the other day. I replaced an o-ring on the fuel rail that was damaged and leaking and now when I put everything back together it wont start. My EEPROM as VATS disabled on it. The oil pressure switch has been removed from the harness so it won't stop this engine from starting either. I can log data from the ECU during crank via ALDL Droid on my phone. The ECU is seeing RPM from the ignition module in the distributor. I wanted to see if anyone has any other ideas of things to check. I will pull the connectors from the ECU tomorrow and verify ground/power to the ECU on all of the pins. I will also see if I can do a continuity test on the two trigger wires from the ECU for both injector banks to see if somehow both wires are broken/damaged. Other than that I don't really have any other ideas.

Things I have done:

Verified spark when cranking
Fuel pump primes before cranking
12v on fuel injector connectors on both banks w/key on
After cranking no fuel on spark plugs they are dry
All sensors new
New Southbay Fuel Injectors and OHM tested all eight of them to 15.8 OHMs
Swapped out the '165' ECU for a second I had laying around
Verified via ALDL Droid ECU is seeing cranking RPM (~150RPM)
Computer is seeing all sensors via ALDL Droid
Swapped out the ignition module in the distributor for a second one I have
Reburned the chip to verify it was ok

GeneralDisorder

iTrader: (1)

Check injector pulse.

If all you did is change an o-ring then it's got to be related to that work.

GD

Tuned Performance

iTrader: (92)

Is it only seeing 150 rpm cranking ?

Aviator857

Verify you are getting spark as it will point you in one direction or the other if you are also not getting spark.

Question is are you getting the pulse but they are not firing or are you not getting the pulse. (Do you have a NOID light?) What is your fuel pressure?

K1ng0011

Yes when I looked at ALDL Droid it showed 150RPM while cranking. I have checked for spark and it is getting spark. I have a mini high torque starter it turns over very quick. Should it have more RPM at crank?

Aviator857

I would personally start by ohming out the wires between the ECM and the injectors if you don't have a noid light to test the injector pulses, based on what you have said. There is a fuse for each bank of injectors but you said you are getting the 12v. Other possibility is too little fuel pressure (or too much air trapped in the line) but these cars usually will purge the air themselves, unless the tank is close to empty.

K1ng0011

I have continuity over both fuel injector banks all the way back to the ECU. Dont have the money for noid lights at the moment. However having continuity should prove that the wires are good. I also tested for continuity on the HEI reference wire back to the ECU and it was fine too. I will keep looking around.

Aviator857

Ask around and see if you can borrow one or check with auto part store loan-a-tool program for noid lights. Also you can get them pretty cheap online.
The part stores do have fuel pressure gauges on the loan-a-tool program.

Tuned Performance

iTrader: (92)

The ecm needs to see 400rpm or higher to enable the injectors.

K1ng0011

I did not think that a starter could turn an engine over at 400RPM. The way I understood it was that once the ECU starts to receive RPM signals from the ignition control module it will enter a cranking state. Where it will fire the injectors for a few miliseconds to get the engine running. Once it reaches 400RPM or so it will consider the engine running and will will send 5v to the ignition control module and begin to control the timing. Also I pulled each of the injector connectors off of the injectors and tried to start the engine with each one disconnected with no luck. That just supports the fact that my injectors are good along with the OHM tests.

K1ng0011

So I got my hands on a can of starting fluid. Sure enough it fired up on the starting fluid confirming that it is a fuel issue. Second I was able to get some help along with a test light (pictures below) to test the injectors during crank. I cranked the engine and had the alligator clip on the positive side of the battery and probed the negative trigger side of the fuel injectors on both banks. As I was cranking the light blinked on both banks which means the injectors should be firing. Doing this should provide the same function as a noid light. My only thought at this point of what the issue could be is low fuel pressure. It must be very low where its not spraying any fuel into the cylinders. However when I press on the schrader valve on the fuel rail seems like there is a good amount of pressure as fuel sprays out. My fuel pressure regulator is new, too. I do not have a fuel pressure gauge on hand to get an exact reading.

K1ng0011

Next things I will do to try and see if I can further isolate the problem is crimp off the return fuel line to see if that increases the pressure and caused it to start. I will also hot wire the pump to run all the time. The third thing I will try is use the test light and run two wires from a fuel injector plug 12v and ground and use the test light to see if the test light is still working. I did test the ground wire during crank and it blinked and I tested the 12v with the engine off and I got 12v on both banks. However I have not tested 12v when cranking doubt its and issue but worth at least testing.

GeneralDisorder

iTrader: (1)

Why don't you just drop a serviceable fuel pump into a gas can, wire it up to a jump pack, and plumb it to the feed line going into the fuel filter. Unplug the factory pump.

GD

K1ng0011

I bypassed the relay to run the pump 100% of the time. I also tried blocking off the return line to the tank. Neither of these things had any effect. I also tested the injector wiring using the following link below. There are no shorts to ground in the injector harness. I also verified that the injectors have voltage during crank. So everything seems to be checking out at this point I am going to see about testing fuel pressure in the next few days.


Injector Wiring Test: https://www.thirdgen.org/forums/tech...ml#post5992754

K1ng0011

Alright got my hands on a fuel pressure gauge. I have lower than 10psi of fuel pressure. Even when I run the pump continuously and block off the return line with a pair of vice grips. So the issue is fuel pressure. I just have to find the cause. I have a brand new fuel tank and fuel pump so I doubt that is the issue but I might be forced to pull out the tank or run a new line to the rail with a jug like GeneralDisorder suggested. I can hear the pump and it sounds like its working so I doubt it is power/ground to the pump but I will check. Pulling the tank is not the easiest job but when I figure out what the issue is I will let you guys know. I also happen to have a second fuel pump laying around that I can use for testing.

JT

iTrader: (1)

Just a quick note for future reference. The oil pressure switch is not there to interrupt engine operation. It is a circuit that will close, with oil pressure, and provide 12volts to the fuel pump bypassing the fuel pump relay. In other words it's a secondary circuit to power the fuel pump - not disable it - if the fuel pump relay isn't working.

Aviator857

What brand fuel pump? If it's a auto store brand it's very common for those to be junk. Also could be a leak in the in tank plumbing.

May have missed this but new fuel sock and filter with the new pump?

And doubtful this is the issue but make sure you have the right pump. TPI vs TBI vs carb pumps have drastically different pressures.

Also could be not enough current to the pump, under load (with pump running) at the tank side check voltage, if not close to battery voltage it could be wiring. The connection behind the rear seat going through the floor has been known to get messed up on these cars.

K1ng0011

I fixed the issue. I went and tightened some of the AN fittings at the fuel rail and filter and I got pressure back. It goes up to 43 PSI or so. My guess to what caused this is when I replaced the fuel injector oring that was leaking I did not disconnect the supply fitting to the rail and it might have worked loose enough to cause a pressure loss. I did not find any fuel leaks but the moment I tightened the AN fittings I got pressure back. What is interesting is that when I was actually leaking fuel from my rail to my intake the engine ran. When I had no visible leaks and pressure loss it would not run. This is a retrofit to a 72 Camaro with a tanks inc gas tank and fuel pump. With a retrofitted TPI setup on my flat tappet 350 engine. I installed AN fittings on the rail and I am running a '165' ECU with a MAP sensor via the OSE12P code that the guys in australia wrote.

Aviator857

Great it was simple. I like to put lines on fittings so I know if it has worked loose.

This is a good example of why it's best to get the right tools and systematically diagnose the problem you could of spent alot on parts swapping.