Hello. Been having an issue over the past weekend. My Dakota is a 93 4x4 auto 5.2l 230k. My muffler has leaked for a good long while, not to terribly bad but i knew its been bad. Was on a 100 mile round trip when 40mi in a loud explosion came from the muffler and killed the engine while cruising. Got out looked under truck, under hood, nothing out of ordinary. Truck started right up and off i went and completed the trip, only difference the pickup was louder. It happens again the next day, explosion, pulled over and started right up and off I went, while returning home it happend for the third time but this time explosion, and wouldn't start, it fired for 2 seconds and died, and ended up getting towed home.


I spend all day troubleshooting. Checked many wiring connectors including the bigger bolt on ones, split wiring harness under fusebbox and re wired splices, tested Tps, map, replaced pickup sensor under dist cap, new wires rotor dist cap, coil, plugs, good compression, good grounds, fuel pump kicks on, fuel pressure is good at the rail tested still hooked up, ASD clicking, have switched relays around several times.

The most puzzling thing is I hooked a spark plug up on wire going from coil to distributor cap and removed to wire from dist and inserted spark plug and cranked engine and the spark jumps a bright blue for half an inch long of a spark so that's good. But I don't have any spark when i pull a plug wire and insert spark plug ground spark plug thread area to negative battery terminal and i don't get any spark, checked multiple cylinders, nothing.

I've checked timing chain play and that seems fine, play in dist shaft, seems normal, its like the coil is getting fire to the rotor but just not at the same time that the rotor is making contact with the dist cap terminals.

So my questions are:

What else could be causing this timing issue? Would the crank sensor cause this? I thought if the crank sensor was bad I would have no spark at the coil?

Could the computer have anything to do with this? Theories?

Thanks in advance any help is greatly appreciated.

Brady

 

My best guess is the timing chain may have jumped, or the distributor is incorrectly positioned. You said you checked the timing chain play, did you completely remove the timing chain cover to check? Did you check to see if the crankshaft and camshaft position marks still line up?

Are you getting any check engine light codes?

 

#1 is at tdc, dist is pointing at #1 and crank Mark is on timing mark so it appears timing is lined up, and hasn't jumped. didn't remove timing cover turned motor back and forth and watched dist movement and doesn't seem sloppy. No check engine light codes.

I feel my only two options would be replace crank sensor possibly? Is there a way to test my crank sensor?
Or possibly the computer. I paid 700 for this truck 4 years ago and hasn't given me a problem until now.

 

Yes it could be the crank sensor. The service manual in the FAQ has the test procedure. Also most autoparts stores can test it for free.

 

Well i had ordered the crank sensor but haven't picked it up since i don't get any resistance on prong 2 and 3 of the crank sensor. According to the service manual it isn't supposed to have resistance so that checks out. I'm at a loss i don't know what else to do i miss my dakota but i'm afraid it's going to end up in the bone yard........ I suppose there isn't any way to test the computer...

 

I once had a problem where I was only getting spark at the coil but not the plugs. It was a bad coil.

 

Really? Did you ever test your coil to see? Do you remember if your spark was blue on your bad coil?

It's really a lack of maintence issue, I knew my muffler was getting bad but I didn't think it was that bad, gas must have pooled in the muffler and exploded but not going out the tail pipe but back into the engine.

The only other things I can think of is:

1. The timing chain jumped a tooth when engine backfired

2. The cam broke and when coil is firing it's just not at the same time that the rotor is touching the contacts on the cap.

3. The computer took a crap, but from what I've read if the computer took a dump, the check engine light wouldn't illuminate at all. But I'm ruling this out because it has to be related to the backfire which stalled the engine and then wouldn't start.

I'm not going to give up, in time I will figure out what it is, I just don't want to keep throwing money at it if the timing chain jumped or something with the distributor or cam got messed. I'm tempted to rip into it today and inspect the timing chain marks.

When I lined the distributor to #1 and got #1 at tdc, I was going to line the crank up but there is 4 notches on the harmonic balancer and nothing to line any of the notches up with! Are the marks ON the timing cover itself on the topside to where I can't see it even?? So this confuses me, chevys i've worked on always had the timing indicator on the side of the timing cover visible from the bottom or the top, and only one notch on the harmonic balancer.

 

One other thing I should note, I get great spark from my coil got it to jump a good half inch. The service manual states:

Primary Resistance: .95 - 1.2 Ohms Secondary Resistance: 11,300 - 15,300 Ohms

My coil Primary: .90 Ohms Secondary: 9,800

Correct me if I'm wrong but, being the resistance is slightly off on the lower end, that should be a ok but it could be problematic if the resistance had been on the higher end? I've heard some people say the Primary/Secondary resistance test is inaccurate/inconclusive though?

If the auto store was open on Sunday I would probably go get a new one and try out, but this coil is only 2 years old.

Thanks.

 

I did find my timing marks on the timing cover where the balancer lines up with. Pulled radiator and condenser to get a view found it under some old grease lol. Had a feelin it was under there somewhere. This week i'll get to double checking the timing and probably pulling the timing cover and making sure everything is kosher. Sooner or later I'll get to the bottom of it, but until then will keep posted to help other first gen dakotaians.

 

Although you already found the timing marks maybe this quick picture will help with your diagnostics. This and others can be found in the FAQ.