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dodge charger falls and stalls slightly when cold. Won't rund when hot.

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Dec 25, 2020
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Location
Phoenix AZ
I've been chasing a problem for months. 1970 charger 440 restored fairly stock. 3000 miles since rebuild 440 and restoration. Stock manifolds, electronic ignition, but changed to Holley sniper EFI after problems with vapor lock. Atermarket AC. Car ran great for 2 years, then one day it ran rought all of a sudden, and I haven't been able to drive it since. When I start the car is runs fairly well. There is a slight hesitation when you accelerate quickly and can lead to a backfire. As the car warms up it gets worse. Car will idle till about 120 degrees and then you have to keep feathering the pedal to keep it running. At full temperature (165) it will only run above 2000 rpm. if it gets below that it pops and backfires and dies. Seems to run smooth at high RPM.

I started changing parts on ignition system.
- coil (2 new ones)
- ingition module
- voltage regulator
- balast resistor
- distributor and timed to stock (5 degrees)
- tested spark plug wires. Replace a few questionable ones.
Then to charging system
- new battery
- new alternator
- replaced battery ground
- added firewall and engine grounds
Fuel system
- cleaned lines
- changed pressure regulator 3X
- sent sniper back to Holley. They said it checked out fine.
- sent Holley data recording. They said it is getting air or missing fuel.
- moved sniper wiring away from ignition system and relocated coil to firewall.
- changed out O2 sensor.
- re-gasketed exhast manifold at block and pipe.

pressure gage at EFI reads 58lbs very steady. When you punch the throttle it moves but only drops a pound or two. Seems the pump and lines seem to be keeping up. All the lines worked fine before. No leaking. Return runs about 1.5lbs of back pressure. I don't imagine that air could come in between the pump and the EFI or I'd see a leak. I've tightened and checked lines between tank and pump. Air getting in the line doesn't seem to equate to the drastic difference between cold and hot. Why would fuel be missing if gage reads well?

The motor has developed a "tick". I think it is from the EFI system. I pulled my valve covers and felt all of the rods and rotated them, no slack. Also ran the car with valve covers off and clearly no ticking at the rockers.

I'm at a loss. Would love to drive my car again someday

engine.jpg
 
I know it would be a hassle but you have spent a lot of time already chasing, would it be possible to put a carb on there and see if the EFI is the problem? It would be nice to know.
 
Can you see fuel coming out of the injectors? How is your timing controlled?
 
I know it would be a hassle but you have spent a lot of time already chasing, would it be possible to put a carb on there and see if the EFI is the problem? It would be nice to know.
thought about that, but sold the carb long ago. Would require some effort to change pump, lines, etc. to get it carb ready again.
 
Yes, injectors seem to be fine. Sent in to Holley and they said it tested well too.
I dont trust anything Holley says. So you can look down the throttle body and see fuel coming out of all 4 injectors?
 
If you can adjust the fuel pressure down to ~7 lbs, you should be able to use the current pump with a carburetor, to do a sanity check. Would it be hard to put a new fuel line from the regulator to a carb?
 
I'm not familiar with snipers but is the software set to behave differently at 120* and 160*?
On my FAST MPI setup there are different temp thresholds and you can accidentally create conflicting commands.
Not sure the sniper gives so much control.
 
From what I can glean you are not controlling the timing with the sniper efi.
To get the full benefits you need to allow the system to control timing.
Then you can adjust everything.
 
I'm not familiar with snipers but is the software set to behave differently at 120* and 160*?
On my FAST MPI setup there are different temp thresholds and you can accidentally create conflicting commands.
Not sure the sniper gives so much control.
Worth asking Holley about. Thanks for the suggestion. I have been reloading the start up settings, so I think they would be resetting.
 
If you can adjust the fuel pressure down to ~7 lbs, you should be able to use the current pump with a carburetor, to do a sanity check. Would it be hard to put a new fuel line from the regulator to a carb?
The pump pushes like 90 lbs and then it’s regulated at the EFI to 58-60 lbs with a return line. I think you would just need to hook up a new pump or attach a device that drops the 90 to 7. Definitely would be nice to rule in or rule out the EFI.
 
It’s always acting up. Can you explain how to test that and what parameters are?
Depending on the coil. Most use a ballast so you should have 7 to 9 volts roughly. You could run a quick temporary jumper from the battery to the coil. You will know right away if it changes any thing.
 
Is the brake booster working normally?
It could be a vacuum leak there or somewhere else.
(165 deg. F is kinda low but that is a different subject)

What is the vacuum reading at idle cold and does it change (drop?) as it warms up?

The tick could be an exhaust leak (which could also get worse with temperature) and if it's on the same side of the O2 sensor it would get an incorrect reading so the EFI might be adding in the wrong amount of fuel.

Just some ideas.
 
Sounds like a typical Mopar ignition dies hot runs cold. Either the pick up or a ecu usually, especially the new no name orange boxes, check it when it is hot and dies. Just fyi
 
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