1. The engine temperature sensor (not the one for the gauge or idiot light) if bad is sending the wrong data to the FI system. If this is happening then the FI system is not regulating the correct air/fuel mixture for outside air.

2. If the throttle position sensor is bad, then again the FI system is not regulating the correct air/fuel mixture for the throttle conditions.

3. You have a vacuum leak, either a hose or a gasket on the intake.

Overall your problems sounds like a fuel starving/lean conditionissue. Have you pulled computer codes yet?

 

Well I just got back from a weekend trip to a couple of mechanic friends to help me troubleshoot the backfiring. We put a good, working TBI assembly from another Ram van on and it didn't change anything. We determind it wasn't an electrical issue, all the plugs are getting spark at the right time, distributor and ignition coil check out alright. The computer read that the van was running lean on fuel. The engine codes we got were...

12 - Recent Battery Disconnection
37 - Open or Shorted condition on the torque convertor
15- Vehicle Speed Signal (Speedomoter still works..)
51 - Lean Fuel Condition
55 - end of codes

After doing several key on, key offs I'm pretty sure that's what it was reading. What direction would you guys be leaning towards? Vaccum leak or bad fuel pump? I think I'm going to rent a fuel pressure guage from Checker tomorrow. Anything else I should try?

Thanks a lot,
Michael

 

A vacuum leak is cheaper to fix than replacing the fuel pump, so I'd hope for that route. Although doing the fuel pressure gauge test first is the best idea. A low reading would kind of confirm that it's the pump, and a normal reading would put you back at a likely vacuum leak. To check the intake gaskets for leaks, start the engine and spray carb cleaner along the intake gasket and see if you get any change in RPMs.

 

Finally gave up and took it in to my mechanic. The previous owner apparently installed some "High performance" spark plugs that weren't firing all the time. Hope this helps someone else.