Stock 383 V2 ~105K miles - no idle and won't run

[mopar_rick]

Guys,

[Update: To close this out - and now for the rest of the story - Turns out, I pumped out the gas tank at one point, but unbeknownst to me, I put more bad gas in from a tainted gas can.  In the meantime,  changed a bunch of other things, and rechecked a few while I still had bad gas in the tank.  One of those was the distributor clocking - I got it in 180 degrees out.  Only after using the gas I pumped out in my lawn mower and having it quit on me, was I able to backtrack to the real root cause. 

Thanks for all the suggestions, she's running fine once again. ]

My 1970 Challenger SE 383 2V AT started exhibiting rough idle at the end of last season over the course of about 20-40 miles. I could keep it running if I rode the gas pedal. The car has been running fine for 15 years.  But this came on pretty quickly.

Over the winter, I did the following and tested between each step. However the engine will no longer idle or run long enough to warm up and refuses to rev up when the throttle is opened up.  The engine will try run for approximately 15 - 30 seconds at maybe 400-500 RPM (that's a guess).

• Sprayed cab cleaner in jets / blew out with compressed air, then reset idle screws.
• Changed the fuel filter
• Changed the fuel pump (gas would spray out of the fitting at the carb when loosened - so I know I had fuel pressure but changed anyway).
• Replaced carb (Holly 2 BBL) with one that was rebuilt several years ago (Carter 2 BBL) and sitting on the shelf.
• Replaced coil.
• Replaced distributor (Rock Auto Replacement), new points, wires, cap, rotor, and spark plugs. Set points for nominal spec dwell
• Checked for vacuum leaks at brake booster and vacuum line, engine compartment vacuum lines for heater/AC control, distributor vac advance line, etc. (haven't check for vacuum leaks in the passenger compartment heater/ac controls yet - but don't hear an obvious hissing noise.
• Siphoned out off the gas and replaced with known good gas. (original gas was no more than a few months old - I run the car once or twice a week over the summer).
• Blew the fuel line out with compressed air, and pulled the sending unit to see if the sock was clogged - looked just as good as when I replaced it.
• Pulled valve covers to verify no bent pushrods or collapsed lifters (Replaced 3 lifters and all valve stem seals 3000 miles or so ago)
• Replace fuel pump push rod on recommendation - old push rod was 0.020 - 0.025" shorter than new one from 440 Source
• Checked torque on old and rebuild carb assy screws found some slightly loose. Tried swapping carbs no change.
• Check engine compartment grounds
• Checked voltage drops in ignition system in engine compartment - found high reading that contact cleaner on bulkhead connector resolved.

When the engine quits running - after 15 to 30 seconds, occasionally a back pressure through the carb will cause a fuel geyser.  Haven't done a compression check, but that's next.

I would welcome any suggestions on what I might have forgotten to check.

Additional notes:

Removed heat riser blockoff many years ago.

[moonshine_mike]

Based on the symptoms, I would have checked the fuel because I have seen similar symptoms in my own Cuda. Especially stuck fuel valve allowing leakage into the bores. However it looks like you have already covered this possibility.
I'm assuming nothing sudden happened that could cause a head gasket failure, like extreme overheating.
-Is each individual plug firing (electric ark)?
-Could the timing chain have slipped or stretched excessively?

[Jay Bee]

What do the plugs look like, you didn't mention checking them. Could there possibly be old bad plug wires, maybe even grounding out. I had to have all my plug wires redone once.

[Brads70]

ballast resistor?

[Katfish]

Check the soft lines on the feed from tank to carb.
Small crack, deteriorated rubber lines maybe.

[mopar_rick]

What do the plugs look like, you didn't mention checking them. Could there possibly be old bad plug wires, maybe even grounding out. I had to have all my plug wires redone once.

Attached is a photo of the spark plugs removed.  Top right is #1.  On first inspect they didn't look terrible, so I didn't spend much more time on them.  Looking at them again, #4 looks a little more crusty.  These have about 3K miles on them.

[mopar_rick]

Based on the symptoms, I would have checked the fuel ... However it looks like you have already covered this possibility.
I'm assuming nothing sudden happened that could cause a head gasket failure, like extreme overheating.
-Is each individual plug firing (electric ark)?
-Could the timing chain have slipped or stretched excessively?

No overheating.  I did recently replace the radiator - it had a very slow leak that eventually became too much of a nuisance. 

I don't recall anything out of the ordinary that would have suggested a timing chain slip. 

[mopar_rick]

ballast resistor?

Ahh, good catch - I forgot the add ballast resistor to the list of things I checked or replace.

I did replace the ballast resistor, and regulator taking care to clean up the firewall at the screw attachment points.

[mopar_rick]

Check the soft lines on the feed from tank to carb.
Small crack, deteriorated rubber lines maybe.

That's a good one.  I'll add that to the check list.  But I would have expected to see some evidence of fuel dripping when I blew out the line. 

[DeathProofCuda]

Seems like you have most of the fuel and ignition basics already covered.  Not sure that I'm completely understanding the fuel geyser that you mentioned.  Is it backfiring (popping) through the carb or is something else happening?  Any chance that the exhaust is plugged and causing backpressure?

I'm leaning toward the timing chain slip. 

 

[larry4406]

What about the timing?

If original chain and sprockets, they are most likely the "silent chain" type coated in plastic.

My '71 383-2bbl in my cuda vert had that (~1983 when I bought it with 100k+ miles) and the timing light was all over the place.

I'm thinking you have skipped a tooth. Friends '68 400 GTO did that and ran like shit or not at all.

[erat340]

If the valve timing checks out, check for a banana in the tailpipe....

[bdschnei]

 "However the engine will no longer idle or run long enough to warm up and refuses to rev up when the throttle is opened up"

That sounds like either a fuel delivery problem with the carb which it sounds like you've pretty much eliminated by replacing the carb or an exhaust back pressure problem which others have suggested. Valve timing maybe but if it starts OK I would doubt that was the issue. So maybe a restricted exhaust somewhere. Does the engine have an ex manifold heat riser valve by chance? Those things used to be notorious for rusting up and getting either stuck open or shut. Stuck open not so much a problem since I'm not sure they were really good for what they were supposed to do. But stuck shut was a problem. Could that be your "banana in the tailpipe" someone mentioned earlier?  :-)

[mopar_rick]

If the valve timing checks out, check for a banana in the tailpipe....

I'll shove the shop vac up the exhaust pipe for a reverse enema. 

[mopar_rick]

"However the engine will no longer idle or run long enough to warm up and refuses to rev up when the throttle is opened up"

That sounds like either a fuel delivery problem with the carb which it sounds like you've pretty much eliminated by replacing the carb or an exhaust back pressure problem which others have suggested. Valve timing maybe but if it starts OK I would doubt that was the issue. So maybe a restricted exhaust somewhere. Does the engine have an ex manifold heat riser valve by chance? Those things used to be notorious for rusting up and getting either stuck open or shut. Stuck open not so much a problem since I'm not sure they were really good for what they were supposed to do. But stuck shut was a problem. Could that be your "banana in the tailpipe" someone mentioned earlier?  :-)

Good question on the heat riser.  I removed that many years ago.  So That's not a problem.

But this is the exhaust system that's been on the car for a long time.  Maybe the innards of the mufflers have degraded and resulted in a clog.  I'll pursue that further.