Hard start from cold

[Boom Sounds]

Grrrrr....

Have you confirmed correct voltage at the injectors and that associated fuses are all good?

[Guyfromiowa]

PeterH - you can buy a reman distributor from Summit Racing dot com for less money that you can buy the individual parts. Look it up as Chevy P30 with 454.


I tried to reply to your DM but got booted off because I am not a 'trusted member'. Three times.


All three of the parts inside the distributor are suspect.


The magnet on the shaft interacts with the pickup coil to provide a voltage signal to the ignition module. The ignition module used that signal to feed info to the electronic control module. The ECM controls the injector solenoids and controls the ignition timing after engine start.


Pay close attention to the distributor shaft position when removing and installing the distributor. You will have to use the 'set timing' connector to keep the distributor in base timing mode while setting ignition timing to finish the job.

[Magnet18]

Originally Posted by Boom Sounds

Grrrrr....

Have you confirmed correct voltage at the injectors and that associated fuses are all good?

Yes, they fire when commanded, they just aren't getting commanded

[Magnet18]

Originally Posted by Guyfromiowa

PeterH - you can buy a reman distributor from Summit Racing dot com for less money that you can buy the individual parts. Look it up as Chevy P30 with 454.


I tried to reply to your DM but got booted off because I am not a 'trusted member'. Three times.


All three of the parts inside the distributor are suspect.


The magnet on the shaft interacts with the pickup coil to provide a voltage signal to the ignition module. The ignition module used that signal to feed info to the electronic control module. The ECM controls the injector solenoids and controls the ignition timing after engine start.


Pay close attention to the distributor shaft position when removing and installing the distributor. You will have to use the 'set timing' connector to keep the distributor in base timing mode while setting ignition timing to finish the job.

I'm not sure how the magnet itself would fail, but the pickup coil makes sense to me. Whats the third part
you're referencing?

Should hopefully be able to check the coil with a multimeter without removing the distributor

[Boom Sounds]

Originally Posted by Guyfromiowa View Post

Guy/Magnet/Peter - can you help my simple English brain understand this?
I can get my head round the distributor sending some kind of signal to the ECM. Once the the ECM senses this signal and some other readings, it sends voltages to the injectors which allows fuel delivery in the TB. If the distributor wasn't sending the correct signal to the ECM, would that not trigger a fault code on the dash?

[Guyfromiowa]

Originally Posted by Magnet18

I'm not sure how the magnet itself would fail, but the pickup coil makes sense to me. Whats the third part
you're referencing?

Should hopefully be able to check the coil with a multimeter without removing the distributor

The magnet is a ferrite core riveted between two iron plates with the pointed reluctor element around it. The magnet fails two ways, it loses it's magnetic force because of the heat inside the distributor and it cracks and flakes away as the ferrite core ages. The center shaft has the magnet built into it and the distributor must be removed from the engine in order to take off the drive gear and slide the shaft out of the casing.


And - the pickup coil is trapped in the case by the shaft/magnet assembly. That means removing the distributor and pulling the shaft to get at the coil. Some versions allow removing the pickup coil without pulling the shaft, but not all of them.



The coil itself is a long, thin wire that reacts with the rotating magnet to produce a small alternating current voltage. The coil fails when the insulation flakes off and the windings touch each other, making it a short, thick wire instead of a long skinny one. The resistance goes down and the output voltage drops as it ages.


A really good pickup coil can generate about 500 millivolts while the engine is cranking. Once the voltage falls below about 200 millivolts the ignition module has a hard time amplifying the signal and switching the ignition coil on and off. Below about 150 millivolts the ECM can not see the signal and will not be able to control the injectors.


In the beginning stages of pickup coil/magnet failure the engine won't start easily from dead cold but behaves better on a warm start simply because the magnet is turning faster and generates a high enough voltage that the ECM can begin normal operation.


IN order to measure the pickup coil voltage output you remove the distributor cap and rotor along with the ignition module. Connect the DVOM or lab scope leads to the two wires from the pickup coil and crank the engine.


You can see that if the coil output is too low the coil and/or magnet have to be replaced. At retail labor rates it is just plain less expensive to install a reman distributor. As a DIY project you can buy a reman distro for less money than buying the parts and you don't have to wait for the job to be completed.


In our shop we ALWAYS tested the pickup signal before dropping in any parts because if the module has burned itself down and stopped working a new module might make the engine start and run, but the new module is doomed. We would be expected to repair it the second time for free and apologize for the failure.


Nobody happy when that happens.

[Magnet18]

That all makes perfect sense, thanks for posting the info!

[Magnet18]

Originally Posted by Boom Sounds

Originally Posted by Guyfromiowa View Post

Guy/Magnet/Peter - can you help my simple English brain understand this?
I can get my head round the distributor sending some kind of signal to the ECM. Once the the ECM senses this signal and some other readings, it sends voltages to the injectors which allows fuel delivery in the TB. If the distributor wasn't sending the correct signal to the ECM, would that not trigger a fault code on the dash?

Guyfromiowas most recent post explains it well, essentially pickup coil voltage output drops as it ages (because the enamel wire insulation is so thin), without a high enough signal from the pickup coil the ignition module won't send any tach signal to the ECU, so the ECU will sit and do nothing. As far as it knows you never turned the key, so it doesn't put out a code, it just sits waiting.

Eventually after cranking awhile you get enough voltage on the pickup coil to signal the ecu and as soon as it catches, you don't have problems because the magnet spins much faster, which makes more voltage overcoming the weak pickup coil

Looked up the coil replacement procedure, yep, you have to totally dismantle the distributor it seems

[Boom Sounds]

Thanks for the explanation. Guy should consider himself an honorary member of our club.

[PeterH-350LE]

Originally Posted by Guyfromiowa

PeterH - you can buy a reman distributor from Summit Racing dot com for less money that you can buy the individual parts. Look it up as Chevy P30 with 454.


I tried to reply to your DM but got booted off because I am not a 'trusted member'. Three times.


All three of the parts inside the distributor are suspect.


The magnet on the shaft interacts with the pickup coil to provide a voltage signal to the ignition module. The ignition module used that signal to feed info to the electronic control module. The ECM controls the injector solenoids and controls the ignition timing after engine start.


Pay close attention to the distributor shaft position when removing and installing the distributor. You will have to use the 'set timing' connector to keep the distributor in base timing mode while setting ignition timing to finish the job.

Thanks a bunch and sorry for not snapping to it early, I frankly didn't understand what you were trying to say. I have to work all the way through issues, so I understand what is going on and you probably already knew that I would find my way to this eventually.
Onward to some testing and needed replacements

[GCinSC2]

School of Hard Knocks remote learning certificate soon to be signed.

[bkahler]

Originally Posted by Magnet18

Guyfromiowas most recent post explains it well, essentially pickup coil voltage output drops as it ages (because the enamel wire insulation is so thin), without a high enough signal from the pickup coil the ignition module won't send any tach signal to the ECU, so the ECU will sit and do nothing. As far as it knows you never turned the key, so it doesn't put out a code, it just sits waiting.

Eventually after cranking awhile you get enough voltage on the pickup coil to signal the ecu and as soon as it catches, you don't have problems because the magnet spins much faster, which makes more voltage overcoming the weak pickup coil

Looked up the coil replacement procedure, yep, you have to totally dismantle the distributor it seems

It would be cheaper and easier to just buy a new replacement distributor. After market distributors aren't very expensive anymore. I bought a new one for my Argosy when I was doing the rebuild.

[Boom Sounds]

Rockauto carry the AC Delco reman for about $200

[bkahler]

Originally Posted by Boom Sounds

Rockauto carry the AC Delco reman for about $200

I probably should have added, the ignition module that came in the new distributor ended up being bad. A Delco replacement module solved that particular problem.

[labans]

I have to agree with everyone who says Buy a distributor. Since it controls multiple functions you really need to have it right and the one you now have is old and most likely worn out. Buy a New one if you can afford it. Nothing wrong with MSD. But spending time on all the other tshooting without proving a perfect distributor is just not good logic. And there is no downside to replacing it. For all the 454's I have worked on in my life as a mechanic I can say that they all ran hot when used in anything other than an Impala or 1500 pickup. Strong running motors, but hot. Heat is the enemy of the internal distributor components.

[PeterH-350LE]

Originally Posted by PeterH-350LE

Yes, now to identify the correct replacement. TPS is new, so I will start with the MAP

I ordered a new distributor, ACDelco, in the mean time the MAP sensor arrived today. I installed it and it fired right up. Injectors doing what they should be doing...Lets see if it holds.
GSL395 lower pressure fuel pump arrived as well. It will be going in this weekend along with the full throttle body rebuilt.

Most likely will install the new distributor and keep the old as a spare.

[GCinSC2]

Is that a win for guyfromiowas suggestion?

Sorry just reviewing from afar.

[PeterH-350LE]

Originally Posted by GCinSC2

Is that a win for guyfromiowas suggestion?

Sorry just reviewing from afar.

No, his suggested cause of the problem (defective pickup coil inside the distributor) was 1 of 4 possible ones. However his explanation was very helpful and very professional.
No one guessed the MAP sensor and only after Nick (Boom sounds) posted the detailed manual, was I able to find the 4 causes for fuel starvation at "cold crank". So the $2.- reward goes to Nick, but he has to pick it up at the Classic MH Rally in Oct 2021

[GCinSC2]

Manifold Absolute Pressure.

Ain’t technology grand.

Points, condenser, a hand choke, vacuum advance and accelerator pumps.

Ah yes the old way.

And I’m petitioning for .6 pt award for his efforts.

[Boom Sounds]

Originally Posted by PeterH-350LE

No, his suggested cause of the problem (defective pickup coil inside the distributor) was 1 of 4 possible ones. However his explanation was very helpful and very professional.
No one guessed the MAP sensor and only after Nick (Boom sounds) posted the detailed manual, was I able to find the 4 causes for fuel starvation at "cold crank". So the $2.- reward goes to Nick, but he has to pick it up at the Classic MH Rally in Oct 2021

Ha - it's almost worth the flight just to pick up the prize. I got up at 4am to watch the cricket (England/India Test match). I'm also applying for jobs, so I might just make it!