Brain fart or bad injectors?

Ok. Jeep sat for a couple months. '89 4.0 RENIX. Ran great when parked. Primed oil pump, reset distributor, started engine......... Idles fine. Just touch the gas and it sputters and pops and backfires. Re-checked distributor, cleaned terminals, new plugs, changed wires and cap, re-checked all sensors... still pops and spits and smells really really good. But idles fine.

Now. I let it idle for a minute, then started pulling injector plug wires off one at a time starting from cyl#6.
#6 - nothing changed
#5 - Noticeable difference engine bogged
#4 - Noticeable difference
#3 - nothing changed
#2 - Noticeable difference
#1 - Noticeable difference

Bad/clogged injectors on 3 & 6? or possibly bad ground causing no pulse to injectors? Bad ECU not sending proper signals? WTF


What do you guys think? Need a quicker than average fix to make it to KOH.

I'm going to change the injectors at lunch, added new 91 fuel, and a little fuel treatment last night. Just wondering if maybe it doesn't sound like the injectors are the problem. Maybe an elec. problem?

Thanks.

Eliminate the harness by swapping the connectors. Swap connectors 5 & 6 and 3 & 4. If there is still no change on injectors 3 & 6 then it is the injectors. If 4 & 5 are now the problem then it is likely the harness or ecu.

WAZZUXJ said:

Eliminate the harness by swapping the connectors. Swap connectors 5 & 6 and 3 & 4. If there is still no change on injectors 3 & 6 then it is the injectors. If 4 & 5 are now the problem then it is likely the harness or ecu.

Click to expand...

See. Brain fart. :doh:


I'll do it at lunch.

no change. Did it two ways. when it was idling, I switched them. Only change was when I pulled 4&5.

Turned truck off. Switched 3&4, and 5&6. Started the truck and it sounded the same. Spitting and backfiring.

Pulled each one individually again...same results. no change when 3&6 are pulled even with the opposite plugs hooked up.

Switched them back to original position, started truck, bumped the gas a few times to see if I can get the RPM's up, and it just backfires... the exhaust smells burnt.

I pulled the vac line from the pres. reg. and the RPM's increased like it should. Changed fuel filter, just cause.

I'm going to swap the injectors tonight just to see what happens.

Sounds like injectors 3 & 6 are bad.

if you need a set to get you out there for the weekend, mine are basically new. well i bought those rebuilt ones from the internet, but never got the jeep on the road. they seem to work real well. i won't be needing them right now so if it helps out with minimal cost......

2stix said:

if you need a set to get you out there for the weekend, mine are basically new. well i bought those rebuilt ones from the internet, but never got the jeep on the road. they seem to work real well. i won't be needing them right now so if it helps out with minimal cost......

Click to expand...

Thanks, but I have quite a few sets lying around. I swapped them last night and had the same results. So I'm not sure wtf at this point.

:wow:

If it sat for a while, put in a can of BG44K and run it for a bit. You probably have a clogged injector or two. If your rig still has the C101 connector, at least pull it apart a reseat a few times.

If you are pulling the injector connector and no change that only means that cylinder is not contributing. It could still be the ignition system causing your trouble.

Pull the injectors, lay them over a piece of cardboard and then crank the starter, see if the injectors are firing or not, or if they are leaking bad

If some of them don't fire you can try a noid light tester to check for electrical signal on the harness. If that passes, get some junkyard injectors to test with.

I don't understand the reasoning behind pulling the dizzy and priming the oil pump, and I can't help but think the dizzy is not indexed correctly.