Hemi won't fire

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easyrider

easyrider

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We have installed a 5.7 hemi in a 1957 Plymouth. Wiring is complete, fuel system complete. Relays energize, Correct power to all sensors and power to coils and injectors. Cranks over but will not fire. What to check next? I'm at a loss.
Tom
 

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Sorry I know nothing about the injection to help diagnose.
Your car looks great, I really like red and the white walls and caps.
Hope your driving it soon.
 
Perhaps its a security issue with the PCM not letting the PCM command the coils to fire? Just shootin from the hip here, but its something to check. Good luck, beautiful car, one of my favorites. Eric L
 
What PCM are you using? If it is an 03 it require 48psi if newer then 58psi at the fuel rail. Normal startup the pump and coil will remain energized for 3-5 seconds after the engine stops cranking. This is determined by the crank sensor sending a signal to the PCM to keep the ASD relay energized.
 
Need a bit more info on what kind of electronics you are using, and transmission.

Something is usually causing the ASD relay to prevent the start up. Could be wrong ignition switch wiring, security feature, or a neutral safety issue.

I agree with all- nice car and color combo. The fins on those cars are just gorgeous!
 
The ECM needs to see the body controller if the ECM came from a car with security system. You need to know a Dealer that can upload an update for a vin number from a fleet vehicle. I got my vin number from a fleet vehicle for sale on E-bay it was a Ram pick-up. Down load a update into your ECM through the OBDII port using that Vin. from E-bay. It will bypass the anti theft and it will start.

My son and I pulled our hair out for 2 Months. You must personally know a dealer to do this . Most will not. The only other way is to put up the cash for a fleet ECM. and you won't know until you try it.

There is no way of knowing unless you are at the dealer and keep trying different Vin numbers as we did. We went through many at least 10-20 until we found one. It was a NY state truck for sale on E-bay. Plain Jane No A/C , P/W or power anything. 2003.

We were using a Painless wire harness.
 
We sent the ECM to Solo Electronics and had the security system deleted. Where does it read fuel pressure? I haven't seen a sensor for that. There is no fuel pressure sensor on the wiring diagram. Maybe I missed that one. That may be the problem. We haven't put fuel in the tank yet. We have the fuel pump relay pulled. We were just squirting gas in the intake to see if it would fire. That worked on my Magnum engine, maybe not on a hemi.

Using everything from a 2004 Dodge 1500. Computer, wiring harness, fuel pump and transmission. Was running before we pulled it, should run now.

Car is Red and White now.
Tom
 

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easyrider said:
We sent the ECM to Solo Electronics and had the security system deleted. Where does it read fuel pressure? I haven't seen a sensor for that. There is no fuel pressure sensor on the wiring diagram. Maybe I missed that one. That may be the problem. We haven't put fuel in the tank yet.
Tom
Click to expand...

There is no fuel pressure sensor .Ford uses a pressure sensor to pulse width the fuel pump for pressure control , but the factory mopar system uses a fuel pump module that regulates fuel pressure to a single line . Most guys use a corvette style fuel filter with a return to regulate pressure.
If you want to check pressure there is no Schrader valve , you have to T in a fuel gauge.
It would be best to get the fuel from the injectors, the fuel may just puddle into the intake.
If the engine has set for a while , the injectors usually will stick closed . The modern fuels are hard on things.
 
Since there is no sensor for the fuel system, if we spray fuel into the intake, it should at least hit if we have spark. That's all we were trying to accomplish at this point. But, we have no spark. We installed stock 2004 dodge pump for this engine in the tank. What do we check now?
Tom
 
This is a aftermarket piece that fits the stock fuel rails and provides a 1/8th npt female port you can screw in a pressure gage or electrical sensor. Since you have the stock pump you should be able to hear it run for a few seconds after the engine stops cranking. If it cranks, then tells you the neutral/park wire is connected. The pump originally was powered by the ASD relay which also powers the coils and injectors. I don't recommend squirting gas into the TB.

 
You can put a spark plug in the coil and ground it and check for spark during crank.
You can also make sure the coil is getting power during crank.
If it is loosing spark, the best thing would be to have a scan tool hooked up checking for codes and data.
And of course proper powers and grounds at the pcm in crank and run positions.
 
Can I ask why you dont just put fuel in the tank and give it a go? The ASD relay may actually be looking for power at the fuel pump relay to fire the coils.
 
ASD is pulled in. We have 12 volts to the coils / injectors, but it drops to .3 when we turn the key to the start position.
 
Do you have 12 volts at run and crank?
 
I know in my 74 Challenger I had to wire the crank and run wires from the ignition switch together so the ECM had powers in both positions. Sounds like your ignition switch has a separate circuit also in the crank position .
 
OK, tied both wires (run/start and run) together and put them on a toggle switch just to make sure we had power in the run position. Starter circuit through the computer. It fired ONE TIME!!Wouldn't do it anymore. We figured out the ASD and Fuel pump relays are dropping out almost immediately. That's why it fired that one time. It fired before it dropped out. Also the throttle motor only works in the start position. It comes on and then goes back off. I guess it is also controlled by the ASD relay. What could be causing the relays to drop out?

Easy
 
I have a 5.7 engine 545 RFE transmission and computer from an 05 truck
I modified the harness myself.
I'm not sure if any of this is helpful, but here is how I wired mine.
I added a relay to power all the run/start functions of the computer using a 12 gauge circuit and 30 amp fuse. This circuit is then split through fuses and smaller wires to power the PCM, brake switch, fuel pump relay, and backup lamps.
The PCM and the relay control input to the fuel pump relay are both powered through this relay in the run and start positions.
The PCM grounds the ASD relay control through a wire from the PCM.
The PCM grounds the Fuel Pump relay control through a wire from the PCM.
I modified the truck fuel pump and my tank to make them work together so fuel pressure is regulated through the pump.
It would not start initially because my injectors were plugged so it was not getting any fuel. Once I cleaned the injectors It fired right off.
I did testing with the pump sitting in a 5 gallon bucket. The truck fuel rail should have a port for pressure testing on the passenger side. I know mine does.
My troubleshooting recommendation is to check for ground from the PCM to the fuel pump relay and ASD relays in the start and run positions.
 
Well I had to think outside the box a little on this one. We have two ECU's from Solo and the security was suppose to be deleted from both of them. I don't think it is and I think that is what was dropping out the ASD relay. I cut the ground wire from the ECU to the ASD and grounded it. The relay pulled in and I fired this puppy up!!
 
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