Ignition.. Pathfinder 88

[pathy88Terr]

So got this bastard to run, BUT it runs only on 1,2 and 3 cylinders when started I can easily pull out 4th and nothing changes, no intake leak.. am a noob at checking the computer. Currently we are 3 people and all 3 are completely lost, it was running fine before cylinder head gasket was removed.

Anything I can get a hint on?

[FirstGenFreak]

Process of elimination

Fuel - is it getting fuel in cyl 4?
Air - valves opening and closing?
Compression - Compression test
Spark - Have you got spark to your spark plug? Check you leads, ignition timing, spark plugs and coil
 

[Slartibartfast]

I would start with spark. Fire on the other three says it's not the timing, coil, transistor, or rotor. Could be a damaged cap, wire, or spark plug.

 

I'd be surprised to find one dry cylinder in a TBI engine. Run it for a minute, pull the plug, see if it's got fuel on it. If it's dry, I would suspect either a forgotten shop towel in the intake manifold that's blocked off the #4 port, or a valve that's not opening. If you're sure it hasn't eaten a rag, pull the valve cover, turn the engine by hand, and see if the rockers for #4 move as much as the rockers on the cylinders that are firing.

 

If it's got fuel and spark, check the compression. If it's low in #4, do a leakdown test to see where it's going.

 

I doubt the computer knows what's wrong. It likely has no idea that anything is wrong--these old systems are much less perceptive than modern stuff. It's easy enough to check, though, apart from the computer being under the seat for some reason. I've got an '89 service manual up on Dropbox. Should be the same as '88 AFAIK.* Start on EF&EC-71.

 

*The real early US-spec trucks, likely 7/'86 to 8/'87, had a slightly different list of codes. Your '88 is outside of that range, but I don't know if that range is correct for the Swedish market. On the off chance you have the earlier computer, 42 is TPS (43 in the '89 manual), 43 is injector circuit (51 in the manual), and 44 is no malfunction indicated (55 in the manual). Again, this is likely irrelevant, both to your '88 and to its current issue--but I imagine a few people have gone mad chasing the wrong code on the early ones.

[Foolstival]

Mate, sounds like a right pain. Have you double-checked the spark plug and wire for cylinder 4? Might be something simple.