Cranking No Start, Intake Backfiring, Help!! | Ford Explorer Forums - Serious Explorations

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Cranking No Start, Intake Backfiring, Help!!

thatkiwikid

New Member
Joined
March 8, 2018
Messages
2
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1
Location
Orlando
City, State
Florida
Year, Model & Trim Level
1999 Ford Explorer XL
Hi all,
I have a 1999 Ford Explorer that I swapped 2001 engine into. Both the old and the new engine are the 4.0L SOHC, old one just blew a head gasket and the lower milage engine was a better deal. So after plenty of late nights I successfully got the truck going, and took it around the block a few times. Started her up a few times to fix some small issues but she was running great!
First major problem I ran into though was my catalytic converters- had the car running around 15 minutes and all of a sudden they started smoking like hell, they were glowing red because they were so hot.
Starter her back up the next day and she ran like a charm for about 10 minutes until she cut out somewhat quickly. Tried starting her again but only a sputter and then it stalled. Since then it only cranks, but it cranks well.
So I started troubleshooting:
-Not the battery
-Not the starter (Just replaced it)
-Fuel Pump Buzzing
-Replaced Fuel Filter, fuel pressure at the rail is good
-Check for spark with old spark plug and wire to ground, spark is good
-Unplug MAF, no change
-Check all vacuum lines, ICV, nothing
-Check all the electric connectors for bent wires or dirt, all good
-Check that weird kill switch under the dash on passenger side, nothing
-Switched the relays around, nothing
-Check for injectors by spraying starter fluid in the butterfly, cranks, cranks, BOOM! Flame shoots out the intake. So... timing issue??
-Replaced crankshaft sensor with functioning one from old engine, nothing
-Replaced camshaft sensor with functioning one from old engine, nothing
-I haven't compression tested it but I figured it's fine since it was running so well earlier
-According to firing order diagram spark plug wiring is correct

The rest is beyond me honestly. I had a mechanic friend briefly come over and have a look, and he confirmed it to be ignition timing. It seems like for whatever reason, the valves are either stuck open on the intake stroke, are not seated properly, or the computer is firing the spark plugs on the intake stroke. I don't know really anything about ignition timing but I read that my timing belt could've slipped a tooth or two, read to check what happens at TDC or something but I don't know how.
I'm also wondering if those catalytic converters burned out my valves from getting so hot and now they don't work?
The SOHC engines don't have a dizzy so it can't be that.
Could it also be wiring or an ECU/PCM issue?
Am I missing anything?
Thanks! Getting so frustrated with this one, usually no starts are pretty easy
frown.gif
 












Next step is check compression on all cylinders. Write down the pressure of each cylinder and post up.
So I got good compression on cylinder 5 but I got nothing on cylinder 6 and 3, so I stopped testing...
 






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