Diving back into my fire project. Fuel+Spark=Nothing? Long post. - Jeep Wrangler Forum
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Old 04-27-2015, 06:49 PM
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Angry Diving back into my fire project. Fuel+Spark=Nothing? Long post.

I have a '90 2.5L manual that was involved in a engine fire with the previous owner. The engine bay got quite hot and fried most of the plastic parts in the bay near the firewall. The air intake cowl for the cab got a little warped and toasted as well. I suspect that when the FD showed up the engine was doused with water and the plastic valve cover was melted and allowed water into the engine. The first thing I did was reseal the engine and flush the motor several times with clean used oil. Sure enough evidence of water contamination sludged out the drain hole. I kept doing this until it came out clean. I also cranked the motor over so that the good oil would be distributed throughout the engine.

I've went through and reconstructed things as best as I can by taking out the old and putting back in with new or used parts. I've replaced most of the TBI components, Air intake, all of the engine bay wiring that was melted, and a bunch of vacuum harness. When the day came I tried to start it and .....tada! It wouldn't start. I discovered that there was no spark or fuel. It turns out the computer was fried so I replaced that. Again I tried to start it and while it had fire and it had spark and it was turning over via the starter somehow magically it wouldn't fire.

So what could cause an engine with both spark and fuel to not fire? I thought of old fuel and squirted a little starter fluid up in the intake just in case. Still nothing. I bought a now coil just in case mine was a little extra toasted and not putting out enough juice. Still nothing. I have yet to do a compression check as my gauge wouldn't fit without an adapter (which I now have). I would think that I would notice something even if the rings were shot though.

That's how it's sat for a couple of months now. I was told that I was obsessing over the Jeep by the boss (wife) so due to both frustration and getting griped at I put it on the back burner. Now I'm back at it.

I've acquired a used engine (another 1990 2.5) that I was told was running when it was taken out for a 318 swap. I'm considering swapping it in to use while I attempt to rebuild and rehab the current motor back to factory new or better specs. I suspect that even if I do that I'll have the same problem...whatever it is.

Any ideas on what this could be?

Oh..and "hi all" and thanks for reading this incredibly huge first post!

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Old 04-28-2015, 02:09 PM   #2
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If you have fuel, spark, and compression you should have ignition. Timing could play a role. Spark is only good if it is happening at the right time.

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Old 04-28-2015, 04:51 PM
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I guess that when it was on fire the vehicle tried to get "underway". Is it possible that this made the timing belt jump somehow?
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Old 04-28-2015, 09:27 PM   #4
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I think the timing belt could be a problem but start with the easier stuff. Get cylinder number 1 to top dead center of the compression stroke and confirm that the distributor rotor is pointed to the number 1 spark plug wire. I am guess that you pulled the distributor somewhere in this process and it is not timed correctly. As Thomas said if you have compression, fuel, and spark it should run but only if the spark happens at the right place in the cycle. the crank rotates 2 revolutions to get through all of the cycles (intake, compression, power, and exhaust). If your spark plugs are firing when the exhaust process is complete rather than the compression process, it will not start.
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Old 04-28-2015, 09:42 PM
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You know....I DID pull it to check it for damage. I forgot about that.

Thank you for possibly pulling my head out.
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Old 04-29-2015, 06:13 AM   #6
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If it ran when it caught fire, and you haven't messed with the timing chain. I would assume the chain is ok. Let us know what you find out on the distributor.
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Old 04-29-2015, 11:45 PM
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Yes it ran, I haven't touched the timing chain.

I should get to it tomorrow at least long enough to check timing and compression.
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Old 04-30-2015, 03:53 PM
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So I got back on the jeep. I took out the plugs to make it easier to spin the crank and was using the starter to get it close to TDC. The good news (sort of) was that it was still timed properly.

The BAD news was that the cylinder closest to the firewall made little rust "puffs" as the engine turned around.

So needless to say the engine is shot. I thought that it might be. The PO wasn't into cars, wokring on cars, basic maintenance... If he'd just have pulled the plug on the motor it would likely have been fine.

Indeed as I started stripping down the motor for removal I came to realize that not just a few, but actually most of the bolts holding the accessories on the motor were finger tight at best. Several of them had so much vibration happening that they were worn partially through.

I do have another 2.5 that is supposed to run. Now I have to decide if its a better idea to use that or do a swap. I'm also loosely considering stripping it to a tub for a full repaint and resto. I have a habit of painting appropriate vehicles OD Green. I'm wondering now if I need a tan or AF aircraft grey color jeep instead of a white one?

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