4.2 RRC was running great, now won't start...

[BDM]

Hey guys,

Apologies in advance for long post. I thought I had a fuel pump issue but after replacing it still having same issues.

It's a 92 RRC with a 4.2 transplant. Had been running awesome. While driving to LA last weekend (about 370 miles) it stalled at the end of the off ramp. It didn't start immediately but after pushing it to side of road and looking under hood and waiting a few minutes, fired back fine. During the weekend it ran fine, no issues. On the way back, I noticed the engine would "buck" in 4th gear while driving up hills. Almost like it wasn't getting fuel or a vacuum leak. Ended up getting home fine and checked for vacuum leaks but couldn't find anything.

While home this week it drove fine one day. At about 1/4 tank it just died a few miles from home in a parking lot. Couldn't get it started again and had it towed back to my house. It just continues to crank.

I've checked all the fuses as well as the inertia cut off relay, all of which are intact.

New fuel pump seems to be working fine. The old one was the original from PO's memory thus my thinking it was the pump.

I ran out of time today so didn't get to check if it's sending a spark to the plugs.

Any thoughts would be appreciated. Thanks!

 

[1920SF]

Fuel, air, spark.

Given that it is a 92 it probably doesn't have a schrader valve on the fuel rail to check pressure but since you have a new pump in there I'd suggest moving to spark.

Check to see if the coil is pushing a decent spark to the dizzy.
Then check to see how the spark looks at the end of one of the wires.

May be time for a new cap/rotor, may be the coil, may be the wires. Worth working through all this systematically.
r-
Ray

 

[Hugh Wilton]

I had a similar problem. Replaced the ignition module & had no further problem.

 

[57loboy]

I am dating myself now as it's been years since I had a RRC w/4.2 but I had this same issue over a number of years when I had a '95 w/4.2. The issue was the same as you describe, initially replacing fuel pump and moving on from there. It was very, very intermittent and a PITA to trace down. If all the usual fuel/spark/air tests come back ok, and if you're using the OEM 4.2 distributor, be sure to check the connections "inside" the distributor for the harness that comes into it. Sven (the member who purchased my first LWB) was able to trace the problem when it popped up for him a couple months after buying mine. I don't recall the exact details, but if you check for threads by me and Sven in the '07-'09 time period within this section, you'll find the details. I had replaced everything from fuel pump to regulator to module to ignition etc. Part of me misses the adventure of driving a RRC on a daily basis....

 

[WaltNYC]

Your comment about "dying at the end of a off-ramp" reminds me of a similar experience of mine ('97 D1). It wouldn't hold idle when it got hot. Turned out I needed a new IACV (Idle Air Control Valve).

FWIW, Napa CRB 21856 (for a 4.0 Jeep) was a suitable replacement. No issues at all since replacement about two months ago.

Obviously your 4.2 is a bit different but the point is that an expensive OEM unit is not always needed.

 

[luckyjoe]

I experienced similar issues with my 4.2L LWB last year, including cut-out, re-start after sitting, and just plain old no-start. 1920 SF is right on the money - verify fuel / air / spark - and there are step-by-step troubleshooting instructions in the WSM. Work with a plan and don't change more than one thing at a time!

In my situation it was the Ignition Amplifier Module still mounted on the distributor. The faulty one would fail to re-start after a long highway trip, or occasionally stall after releasing the accelerator. Short trips would re-start, long trips needed time to cool down. The first step I would recommend is to check that the two tiny bolts securing the module are in fact tight. If they are not you can get an intermittent ground that will also result in stalling/no-start (even with a known good module). When replacing the Module, make sure to use a judicious amount of thermal paste between the module and distributor body.

To complicate issues, I also suffered a faulty coil-to-distributor wire, only 5 months old, masking the no-spark culprit. I spent a LOT of time tracing and checking every wire in that ignition and FI system, and spent a LOT of time reading and searching through Dweb archives. After I had it up and running reliably I relocated the ignition amplifier module OFF the distributor. Happy camper and now more well-versed in the 14CUX ignition!

 

[BDM]

Thanks for the feedback fellas. The PO did the IAM remount on the fender, however not sure how old the actual IAM is. Going to check with him, do some spark tests and report back.

One caveat, it has been pouring rain here for nearly 2 weeks straight. I didn't notice any of these symptoms until it started raining heavily on the drive back from LA.

 

[1920SF]

As an aside, check the grounds...as many as you can find.

 

[kk88rrc]

Moisture in the dizzy cap maybe?

 

[BDM]

Got it. After wrestling through what seems to be a cluster of wires in the engine bay from one of the previous PO's, I found that the wires going into the distributor were completely ripped out! First I tested for a spark and found none, then more looking revealed the ripped out wires.

Part of the wiring harness had tangled around the steering shaft so turning only exasperated the problem. So, I had to sodder and shrink wrap the wires back together. PIA but the truck is back running again. Only problem now is that it seems to idle like shit! I guess I'll have to go back and check wire connections and vacuum lines etc.

Thanks for all the help guys!