Have a 1989 F-700 with 429 factory propane engine----problem is engine cranks but cuts off after warming up for 5--6 minutes. Will not recrank until engine cools down. Starts fine----just will not run after it warms up. No fire from distributor after it quits.

Have replaced coil, ignition module, ignition switch, complete distributor and battery. Have checked voltage to + side of coil----reading 7.8 volts while running-----and as engine cuts off, and after engine is dead.

Asked some questions relating to this problem sometime back in the fall----but can't find the thread now. Just now getting back to trying to sort out the problem---don't use the truck on a regular basis, but need to get to going now.

In the earlier thread----someone figured I had "ground" problems. I have not been able to find any hot (heated) ground connections or wires.

I have also run a hot wire straight to the + post on the coil---still cuts off.

Question:
(1) How can I test the pick up coil in the distributor (even though its new)??
(2) How can I test the ignition module???
(3) Does the distributor body ground to the engine block---could the distributor not be getting a clean ground to the block and therefore heating up the pick up coil?

I had changed the starter out imediately before this problem first occurred---cranked truck and left it running for a few minutes. It cut off after sitting at low idle for a few minutes. One thing I notice----it seems to run a little longer during the cooler temps for right now versus warmer weather back in the early fall. Could I have inadvertenly broken or pulled something partially loose on installing the starter?

Any ideas or suggestions realyy appreciated----I am "bumfuzzled" as of now. I am relatively familiar with this ignition system----having run a '84 Bronco for over 300,000 miles with the same system.

Delta Dirt

 

Have a 1989 F-700 with 429 factory propane engine----problem is engine cranks but cuts off after warming up for 5--6 minutes. Will not recrank until engine cools down. Starts fine----just will not run after it warms up. No fire from distributor after it quits.

Have replaced coil, ignition module, ignition switch, complete distributor and battery. Have checked voltage to + side of coil----reading 7.8 volts while running-----and as engine cuts off, and after engine is dead.

Asked some questions relating to this problem sometime back in the fall----but can't find the thread now. Just now getting back to trying to sort out the problem---don't use the truck on a regular basis, but need to get to going now.

In the earlier thread----someone figured I had "ground" problems. I have not been able to find any hot (heated) ground connections or wires.

I have also run a hot wire straight to the + post on the coil---still cuts off.

Question:
(1) How can I test the pick up coil in the distributor (even though its new)??
(2) How can I test the ignition module???
(3) Does the distributor body ground to the engine block---could the distributor not be getting a clean ground to the block and therefore heating up the pick up coil?

I had changed the starter out imediately before this problem first occurred---cranked truck and left it running for a few minutes. It cut off after sitting at low idle for a few minutes. One thing I notice----it seems to run a little longer during the cooler temps for right now versus warmer weather back in the early fall. Could I have inadvertenly broken or pulled something partially loose on installing the starter?

Any ideas or suggestions really appreciated----I am "bumfuzzled" as of now. I am relatively familiar with this ignition system----having run a '84 Bronco for over 300,000 miles with the same system.

Delta Dirt

 

Pickup test: Disconect the neg. bat. cable. Connect your ohm meter to the two leads to the pickup. Resistance must be within 400-1000 ohms. If not, replace the pickup.....been there.

Coil test-Primary: Disconnect the neg. bat. cable or disconnect the neg. wire on the coil. Read with your ohmmeter between the positive and negative terminals on the coil. Resistance should be less than 1-2 ohms.

Coil Test-Secondary: Measure with your ohm meter between the neg.terminal on the coil and the secondary output terminal/tower on the coil. Should be between 700 and 12,000 ohms. If you read infinity or very low resistance, the coil is bad.
Hope I could help.

 

Delta, obviously you have a heat related problem through ingition.

Is there adequate space behind the module for cooling the back of the ingition module when it is mounted ?

You have replaced parts you didn't need to.

You need to check the Pick up module in the distributor and look for partially broken or frayed wires leading to the distributor.

How good is the battery for condition ?

DSII requires at least 8.2 volts to operate properly.


SLS,
Instead of typing it out everytime you can use this page which I have access to on my web page.

http://www.fluke.com/application_not...AGID=1&SID=103

 

Cool!
Thanks!
It appears you are referring to 8.2 at the + side as mentioned, correct?
Nice information. Thanks.

 

Here's how I've isolated heat related problems in the past. With engine cold remove the ignition module and heat it in your oven for about 20-30 minutes at 220 deg. F. Quickly put it back in vehicle before it cools and see if the truck will start. If it doesn't, you've found the problem. If it does, use same heat soak procedure on coil. Still starts? Then use a heavy duty hair dryer (or better yet a heat gun) on the pickup coil in the distributor. One of the three is usually the defective item. The Black/Light green wire from the distributor to the ignition module is the ground wire.

 

It's going to be hard to test this since it's heat related.

One other test you can do is put your + voltmeter probe or testlight on the negative or tach terminal of the coil, and put the negative of the voltmeter or testlight on the engine block. As you crank the engine, the voltage should jump up and down. This is telling you the system is turning the coil on and off. Then let it quit, and do the test again. If the voltage is not going up and down, you know the system is not turning the coil on and off. Just another verification of what's going on.

What you might try is let the system cool till it will start. Crank the engine to verify it will start, and then shut it off. Take a hair dryer and heat up the ignition module. See if it will start. If it does, shut it off, and take the dist cap off, and heat up the pickup coil. Put the dist cap back on and see if it will start. You could try some of the connectors too.

If you happen to find something with the hair dryer test, I would do it a couple of times just to make sure that's the problem.

 

Does this system on your truck start on gas and fuel injectors and then after it has ran for a few minutes it will switch over to LPG, change the timing and shut down the injectors automatically?

In other words we need to know if you have a duel fuel system.

 

Thanks for the replies----hope to work on it again tomorrow. Will utilize the various recommendations on trying to isolate the problem. (have already confiscated the wife's hair dryer)

Battery is new and voltage is good. Engine is straight propane----no injectors involved. Very simple set up.

I bought the truck used and jumped into changing the different parts out with the idea that at least I would know that this particular part (etc.) would be new and in good shape for the future. Do know that it had a Fred Jones remanufactured engine installed not to long before I purchased it-------so I really don't know for sure that everything is back in place as it should be. Don't run it much----but it had been "running like a sewing machine" before changing out the starter.

In regards to the ignition module----it is mounted flat against the fender well, same as my old '84 Bronco. Should there be a spacer to provide open air space for cooling behind the module? I presume that the module grounds itself through the wiring harness. Presuming that the module is not depending on ground through the fender well. Could it be that the module is not getting proper ground connection through the fender well?? ---since the main outer fender shell is fiberglass. But seems like in the past---I have changed out ignition modules and cranked the engine for test purposes without mounting the module down to the fender well.

Will come back and let ya'll know what I find to be the problem (if I solve it). That way----might help somebody else down the road. Will check this post again tomorrow morning before going to shop in case any more ideas come along. Thanks for the help.

Delta Dirt

 

The module gets it's ground through the black wire going to the distributor.

 

See nowhere you say that you checked for spark and you have also have seemed to have changed out all of the Ignition System items so I will guess you have spark when it cuts off.
You said "No fire from distributor after it quits". I am guessing that this is an assumption.

You talked about the fall and now with the problem so I am guessing it would run fine in the heat of the summer.
With that said I would say you have what I call regulator freeze up. Have seen this happen a lot of times on straight propane rolling stock.

If this is what is happening you might try raping rags soaked in hot water around the regulator until the cooling system hoses that run to the regulator warm it.

This is why most propane trucks have a duel system to warm up the cooling system to prevent this.

 

Subford---

Believe its an ignition problem----no frosting on the vaporizer (as I first suspected). Too eliminate the vaporizer----I switched over to a vapor line, just to fully eliminate the fuel system. Still same problem----then went to coil, etc.

Glad to know you have some propane experience---I have run a lot of propane trucks and tractors in years gone by.

I am not getting any fire from distributor (plug wires)-----nor from the high tension wire from the coil after it quits. Plug wires were replaced new last spring with a tune up on the truck at that time.

Am going to the shop in just a few minutes to get started on getting this problem resolved (hopefully). Hope to give ya'll an answer tonight. Thanks

Delta Dirt

 

NOTE: in the foreground how much space there should be behind the Ignition module for air flow.

 

Today's report---

Truck would not crank at all-----partial ignition, but never hit off. Checked fire from coil high tension wire and it was sparking once on initial crank over-----then no spark until turning off switch (at which point it would spark once or twice with real weak fire).

Checked coil----it checks OK.

O'Reiley's parts house said that they could check ignition module----took both the original module from the truck, plus the one I purchased at NAPA back in the fall---and they both checked bad. O'Reiley's didn't have this particular module in stock and NAPA was closed-----so will go back to NAPA and get ignition module swapped out Monday.

Am I right with my thinking the "breaking action" (as in the old style points) comes from the ignition module?? (has always been my understanding)

I only have one hot wire going to the + post on the coil-----reads 7.8 volts in run position. Mil1ion stated that the Duraspark II system needed 8.2 volts to operate correctly. Is the 7.8 considered too low voltage??

Also Mil1ion---I just saw your photo on air clearance. The module has been mounted on the curvature of the fender well----may not be getting full air clearance as you have illustrated. Will try for a flatter mounting surface.

Any more thoughts are surely appreciated. (Will test new module before installing)

Delta Dirt

 

I have Duraspark II system on two of my trucks (77 & 83) and neither one has an air gap under the module and never did have one. Solid contact to the inner fender will dissipate more heat than the hot air from the radiator in our 100+ Kansas heat. I would not use any module from an auto parts store, only Motorcraft if I have to get one from a salvage yard. The 83 has only had one replaced since it was new, (I bought it new) and the 77 has never been changed in the 21 years I have had it.

The voltage at the coil depends on the battery voltage, the volt drop across the resistance wire to the coil and how much resistance the coil has back to the negative side of the battery. Any of these can change the voltage reading you get and since the truck is not running the battery voltage is more than likely lower than normal.
You should have Battery Voltage at the coil while cranking and the other side like Franklin2 said should be flashing while cranking.

Yes the "breaking action" does come from the ignition module and the signal from the pick up in the distributor just goes to the ignition module.