Hey folks,

I have been helping diagnose a friend’s 1985 RN5 PU Pickup. The truck started having intermittent starting problems that developed into a more consistent problem. My friend was able to push start it and drive it to a shop where it has been for a while. The starter was turning over the engine well, but initial conclusion was that there was that there was no spark, so eventually, after a variety of diagnostics, the the ignition control unit was changed, without success.

The other day I went over to help the mechanic(he’s also a friend). He had found the night before that there actually was spark, so we refocused on making sure the timing was right. I manually inspected the distributor was aligning with the correct stroke and TDC, the timing chain was in good shape and the valves were opening at the correct timing. I also checked the #1 piston was on time with TDC, looking through the spark plug hole. We sent smoke through the carburetor and ensured flow through each intake valve. The spark plugs had some sign of fuel, but the pistons look fairly dry. We confirmed the fuel solenoid was clicking when attached to the battery.

We decided to put new spark plugs in and check the spark. It turned over strong, but with an irregular heave. There was spark on all cylinders. It seamed weak, though, so we put a new coil on. It still seam a little weak. We decide to test the timing with a timing light. The timing was very off(I was running things in the driver’s seat, but I think it was a quarter turn advanced). The distributor was still lined up. At this point it started turning over with out the heave. We play around with adjusting the distributor, but the timing was too far off for the normal adjustments. Taking the whole distributor out and turning it to the next tooth rotated it too far. Then the timing light stopped flashing and we lost spark. We called it a night.

So, it seams as though the we have an intermittent spark problem that is off timing, and possibly still not enough fuel. Anybody have ideas? Is there any thing we should test on the ignition system and ignition control module?

Thank you all,
Joe

 

Any work done before the problem first started? Have you checked valve lash?

 

No major work that I'm aware of. It was a consistent short distance commuter before it went into the shop. I think the starter was replaced half a year ago after it was burnt out from being stuck on. It would be good to check the valve lash.

 

Here is an update:
The truck is running, but it needs some carburetor work as the only way to keep it going is to hold the throttle open.

Turned out that the reason we lost spark was due to a faulty connector between the inductive pickup and the ignition module. The paddle connector had been pushed into the back of the plastic part. Once that was connected it had spark, but was about 30º advanced. I was able to get it on time by sliding out the distributor and rotating it a tooth over. The thing is now when you line up top dead center and remove the distributor cap, the rotor point 30º retarded(in the photo my light bar is showing the angle It should be at to line up with the contact).

Does anyone know if this is normal? Should the spark be jumping from 30º before the contact or is there supposed to be a delay in the coil that isn’t happening. I know on the VW bug if you put the timing light’s pickup before the coil it is more advanced than the distributor wire.

Thanks!
Joe


After timing the rotor is retarded when visually inspected. Green connector in the background was not actually connecting.