Engine starting issues (440 Mopar)

[1970CUDAAAR]

Hi!
I need help to identify the followiing issues:

I have a 440 mopar with a Holley EFI (version 1). The engine cranks verry well but fail to start most of the time and when it start it runs verry roff. Holley help me to reprogram the EFI and still have tha same issues. Holley tells me that most probably my problem is due to having to change the sparks plusgs.

Do you people suggest other issues that could cause this situation. Eg - coil - distributors Etc. Thanks!

 

[Challenger RTA]

I know nothing about the Holley EFI. I would think someone here does. Hang in there someone will know.
The question I have did it run fine before you installed the EFI?
Check power, grounds and all connections. Fuel filter, regulator?

 

[pschlosser]

In principle, the Holley Sniper EFI is a glorified carburetor. Even if you had the factory carburetor on the 440, if it didn't start, you would need to go through checking out the various system to figure out why.

The Chrysler 440 engine is nothing special or unique in this context. The same troubleshooting methods apply to V-8 combustion engines, regardless the engine type. This means, you can use help and advice from other sources.

Is there a vacuum leak?
Is the engine timing set correctly?
Is the distributor in good working order?
Are you getting spark?
Do the spark plugs look good?
Is the coil within spec?
Is the coil getting the correct power?
Is the Holley EFI getting fuel?
Is it getting the correct fuel pressure?

We need to figure out why it runs roughly once it DOES start.

 

[moparleo]

Diagnostics 101. Is the battery fully charged ?
Have you removed the spark plugs to check them for fouling etcc...?
Listen to the people who made the product, Holley.
Worst thing to do is get a bunch of different opinions or guesses.
Follow along with Holley's suggestions first.
Nobody here, is there to inspect what you have to give a qualified guess.

 

[1970CUDAAAR]

Thanks for your advice. Finaly I got the plug replaced and the car runs good. However we notice that the plug are completely black probably due to running verry rich. We took the oportunity to do a compression test and it makes me worry:

Passenger side = 125-110-110-110
Driver side = 95 100-100-100

My mechanic tells me that it could be due to having to adjust the valves.

Is their anything I should do with the EFI adjustment to resolve the "running rich"?

Any comments on this - thanks!

 

[pschlosser]

We took the oportunity [sic] to do a compression test and it makes me worry:

Passenger side = 125-110-110-110
Driver side = 95 100-100-100

My mechanic tells me that it could be due to having to adjust the valves.

the OEM setup of the lifters uses hydraulic lifters. these "pump themselves up" like a body builder, and don't require adjustment. But I don't know what you got under them valve covers.

Losses of compression come from two common sources: worn rings, and work valve seats. There is a way to distinguish one from the other.

This is the procedure as I recall it:
1. perform tests on a cold engine. preferably one that has been sitting for a few days, so there is minimal oil on the cylinder walls and valve seats.
2. remove all the spark plugs.
3. test and record the initial compression on all 8 cylinders.
4. squirt about 20cc (a tablespoon) of motor oil into each cylinder before testing anew.
5. test and record each cylinder (injecting the oil before each test)

the added oil temporarily allows worn piston rings to seal better for a small number of revolutions.

the cylinders with higher compression after the oil is added generally means worn rings.
the cylinders with no change in compression (presuming it's still low) points to worn valve seats (maybe guides, too.)

 

[1970CUDAAAR]

We did the compression test one cylinder at the time without removing all the plug. Is this an issue that could cause the test to be wrong?

 

[pschlosser]

Thanks for your advice. Finaly I got the plug replaced and the car runs good. However we notice that the plug are completely black probably due to running verry rich.

Is their anything I should do with the EFI adjustment to resolve the "running rich"?

The software settings on the Holley EFI directly control the AFR (air-to-fuel ratio)

But there ARE other causes of fouled plugs:

restrictive air flow (dirty air filter)
vacuum leaks
worn piston rings (failing to squeegee the oil from the walls)
work valve seats (allowing oil to get sucked in on the intake stroke)
other sources of excessive oil in the cylinders during combustion (example: worn valve guides)

The Holley EFI is supposed to know the AFR by an oxygen sensor in the exhaust flow. If this is absent in your setup, (presuming it can function without it) then you'll want an external tester to confirm the AFR is correct and/or within spec.

 

[pschlosser]

We did the compression test one cylinder at the time without removing all the plug. Is this an issue that could cause the test to be wrong?

not usually. removing and replacing the spark plugs one at a time will be fine.

depending on the type of exhaust system blocking your access, removing the spark plugs can take longer than performing the compression test !

 

[Bret Schneider]

A leak down tester is usually the best tool available to diagnose low compression issues. Not overly expensive for a decent one. Might check the auto parts stores and see if they have one available in their loaner tool arsenal.
The Holley Sniper EFI system is self learning. When the engine temp is cold the system remains in open loop and bases the injector dwell time primarily on the engine temperature. BTW this is why it's important that the fuel pressure is correct. Since there's no O2 feedback yet the system is adjusting injector dwell time assuming the pressure is where it's supposed to be. Once the engine temp nears the operating temp it'll enter closed loop and start adjusting the injector dwell as needed to maintain the correct A/F ratio. Typically it'll take a few cold starts for the system to "fine tune" itself so maybe that's part of the reason for the blackened spark plugs you saw. You might want to pull the O2 sensor and check that as well. Probably as black as the plugs. After a few cold to warm cycles the system should start to dial itself in and the idle will improve.

Although those compression numbers you quoted are concerning. If this set of plugs fouls up as quickly as the first set you will likely have to address the compression problem.

 

[Deathproofcuda]

Considering those compression numbers, are you certain that the black plugs aren't due to burning oil instead of running too rich? If you are burning oil, I can't imagine that the O2 sensor would last very long.

 

[heminut]

We did the compression test one cylinder at the time without removing all the plug. Is this an issue that could cause the test to be wrong?

The most accurate way to do a compression test is with all the plugs out AND the throttle blades held wide open.