5.7 Hemi Swap Tech question

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smackhonda

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I put a 5.7 hemi in my 68 dodge dart and Im having some problems with the engine. It will not fire the injectors while it is cranking. If I give it a shot of ether it will pop off and then the injectors start to fire. I have power to the injectors, the computer just isnt grounding them out when they are suppose to fire. Ive tried to trick the computer into thinking it was running and still no injectors. Is anyone familar with the 5.7 wiring or has a clue what would cause this? Also while the engine is running, i have no response from the foot pedal. I have 2 ecm"s. One that came with the harness I ordered for this build and the original one from the donar vehicle. Neither will work right. Feel like something is missing from the harness I ordered. Please help!​
 
You might get more replies in the new hemi swaps thread.

I don't know if this is any help, but one thing that comes to mind is to check the ASD relay.

Where did you get your harness?
Do they offer any support?
 
boden said:
You might get more replies in the new hemi swaps thread.

I don't know if this is any help, but one thing that comes to mind is to check the ASD relay.

Where did you get your harness?
Do they offer any support?
Click to expand...
Yes it does sound like the asd relay or the wiring to the ignition switch. If you have it wired wrong it will drop power to the pcm while cranking. I would also look into whether the pcm has skim enabled.
 
Another thing to consider is that the Throttle will only operate if the engine is running so if you try to get the throttle to open when the engine is off it wont move.
 
I got the harness from plumfloored creations along with the pcm. Ive had nothing but troubles from this company. Worst experience ever!!! It took a year to get all my parts after I paid for them. and some of the parts are wrong. Its impossible to get a hold of any one there. A lot of the plugs were wrong on the harness, luckally I had the harness out of the donar vehicle. Ive went through the wireing a few times to make sure it was right. I will look into the ASD relay, I messed around with it a little but I wasnt really sure if it was suppose to be powered or not powerd while cranking. I tried both with no results. As much problems as ive had with this harness, the asd relay could be wired wrong. Wish I had a wire diagram for this harness. I have one for the donar vehicle but the colors are all wrong. Let me know of any other ideas? any thing helps at this point.
 
Also how would I be able to tell if the pcm is skim enabled? I seen on one of your post on the hemi swap thread a chart on the harness johnsparts. It list a brake switch. Does a brake switch have to be wired into the pcm to make it run? This harness I bought from plum floored doesnt have any tags for a brake switch.
 
That was actually my chart that johnsparts reposted. If I remember correctly, I think the brake switch is just necessary for the trans to work correctly. To check the ASD relay you could trace the wires from the pcm. Attached is what is listed in the 05 truck service manual. Notice the ASD relay output goes to both pin #19 and #28
 

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Thanks boden, when I get home from work I'm going to try a few things. Its my goal to get this running right this winter so I can get the car to paint this spring.
 
Just a thought, but the ignition switch doesn't power the same wires during start and run. If you only hook the new harness up to one of the wires, it might give you problems. I know you have to hook both the blue and the brown wires at the ballast resistor to the harness on a Magnum SMPI swap. Maybe this is only a later A-Body thing, but thought I would throw it out there.
 
smackhonda said:
Also how would I be able to tell if the pcm is skim enabled? .
Click to expand...

You need the ALDL connector tied into the ecu to pull codes and data with a scan tool to see if there is a fault in the security sytem . It will list skim on data screen.
 
I went through my wireing and tested alot on my computer tonight. I have power going everywhere there is suppose to be power, and grounds everywhere there is suppose to be grounds, on run and start mode. I have a signal from my crank and a signal from my cam. Getting oil pressure signal. The codes it is setting is , low volt IAC , Intake air temp, o2 sensor down steam( which im not useing), battery temp, a/c comp, fuel level, once in awhile a oil psi code will pop up while cranking, but i have a manual ga and it has plenty while cranking. I dont think any of those would keep it from fireing the injectors. I checked my ASD relay and its working properly. Im starting to think that something isnt programed right in my computer. THis is a special computer I bought so I could run my 727 tranny. The company that I got this from will not return email or phone calls from me. so thats out of the question. Any other advise? Thanks!!
 
It sounds like the ECU isn't getting power while cranking and that's why it won't stay running until you switch the key back to on. Check to make sure it's staying powered up during cranking and then go from there is what I'd do.
-Jon
 
Are you sure the injectors are not being grounded or are they just not providing fuel. A buddy put one of these in a street rod and ran in to a similar situation. Turned out the fuel rails wound up being gunmmed up with old fuel from sitting for a couple of years while they were assembling the parts to put it together.
 
That's not the problems. I have power going where it should during cranking and the run position. I have a noid light in one of the plugs 4 the injectors. I've tested the power several times and I got power to the injectors during cranking and the run position. the computer is just not grounding them.
 
I don't know if this is any help, but this is from my 05 truck service manual.

ENGINE START-UP MODE
This is an Open Loop mode. The following actions occur when the starter motor is engaged.
The PCM receives inputs from:
- Battery voltage
- Engine coolant temperature sensor
- Crankshaft position sensor
- Intake manifold air temperature sensor
- Manifold absolute pressure (MAP) sensor
- Throttle position sensor (TPS)
- Camshaft position sensor signal
The PCM monitors the crankshaft position sensor. If the PCM does not receive a crankshaft position sensor signal within 3 seconds of cranking the engine, it will shut down the fuel injection system.
The fuel pump is activated by the PCM through the fuel pump relay.
Voltage is applied to the fuel injectors with the ASD relay via the PCM. The PCM will then control the injection sequence and injector pulse width by turning the ground circuit to each individual injector on and off.
The PCM determines the proper ignition timing according to input received from the crankshaft position sensor.
 
Thanks boden. That's pretty helpful. I talked with dave webber yesterday. He gave some helpful advise too. Getting closer to figure in this out.
 
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