DMG

98 3.4 truck had a fire, I replaced the entire dash and body harness. Everything works, fuse and relay centers were replaced too but the truck will crank and barely run for a few seconds before puttering out.

There are codes for maf and igniter. Both are getting power. I swapped them with known good units from another truck. I ohmed out the wires back to the PCM and they were good.

I know I am missing something. Not sure what.

Also, the truck did not have cruise control. The new harness is from a truck with cruise. Could that be an issue?

Could the harness have a different pin out?

wyoming9

iTrader: (1)

Did you also replace the engine harness??

Did you use the ECM with the harness??

Or use yours if so was the harness out of the same year and trans??

The cruise control on both mine are removed and it makes no difference.

vital22re

iTrader: (2)

Cruise has no bearing on it running. Will it stay running on starting fluid? If so then you have a problem with wiring to the circuit opening relay. What year harness did you use? And from what?

DMG

I used a harness from the same year. I replaced body and engine harness. I bought another PCM and it didn't change anything.

I seem to be getting power to the maf and igniter which indicates the circuit opening relay is working, correct?

vital22re

iTrader: (2)

Nope. Maf sends a signal to the Cor to kick on the fuel pump when it senses engine is pulling vacuum *starting*

vital22re

iTrader: (2)

Is it the old style maf? giant inline tube? or the drop in style?

DMG

Big inline tube type.

DMG

Ok. I had that backwards.

wyoming9

iTrader: (1)

The second ECM was it known to be good??

Do you have the diagnostics for your 98 engine?? So you can check the ECM and the igniter and the MAF

vital22re

iTrader: (2)

The wiring for that comes directly through the engine harness that you replaced. Its possible that your new harness may have been early 99 in which case the pin out at the maf plug would be slightly different. However the Igniter pin out at the plug I believe is the same. Are you sure you have all your grounds hooked up on the harness? Maybe both maf and Igniter are missing the grounds it needs from the ecu which it gets from the engine harness.


Try starting and running the rig on starting fluid. If it will cough sputter run then we can at least know its not getting fuel.

DMG

It runs on ether. What wire should feed the fuel pump?

vital22re

iTrader: (2)

Find the location of the COR *circuit opening relay* It powers the fuel pump. But it needs a signal from the MAF.