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Old 02-26-2019, 05:34 PM   #1 (permalink)
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78 Wagoneer stalls after warms up and runs for 10 min

specs
78
Wagoneer
360 stock with motorcraft model 2100-2 venture carb.
new plugs and wire
new cap and rotor
new Coil
new starter and relay and cables
new P/S Pump and steering box and hoses

I rebuilt the carb myself it was missing the accelerator pump spring so I had to buy a holly accelerator pump spring assortment and pick one that looked like it fit. don't know if it needed to be a certain spring or it could be any spring as long as it fit properly.

she starts up fine press gas pedal twice and she kicks into higher rpm while it is cold and rpm drops when warm and I tap the gas pedal it idles fine so I guess the choke is working but after I let it run for about 10 mins she starts to run rough then dies. she restarts ok but still runs and idle rough then dies also when I raise the idle up a bit it will act like it is bogging down then smooths out a bit then goes rough again.

there will be times when it stalls and she will not restart sound like no spark when I crank the engine over it spins but no fire except when I release the key I get a slight sound like she wants to fire but only when I release the key I and getting a good electrical reading from the switch so I don't think it is the switch but I could be wrong. After she sits for a few hours she will start fine and cycle stars all over again

kind of sounds electrical but I have all new parts except wiring but I am getting voltage when I am supposed to and when I am not.

Any ideas?
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Old 02-26-2019, 06:23 PM   #2 (permalink)
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Sounds like it could be a vacuum leak
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Old 02-26-2019, 07:01 PM   #3 (permalink)
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Thermo switch controled vacum leak*
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Old 02-27-2019, 07:23 AM   #4 (permalink)
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"...she will not restart sound like no spark when I crank the engine over it spins but no fire except when I release the key I get a slight sound like she wants to fire but only when I release the key..."

This is the classic symptom of a dead Motorcraft ignition module. 10 minutes running then stall. Spark on key release.

These modules are a high failure rate item. The genuine Jeep/ Motorcraft ones are better than the others if they are still available. Avoid chi-com made ones if at all possible. Should have a blue strain relief where the wires go into the module.

I would find and keep a good spare in your glove box. Some of my customers stacked them using threaded rod instead of the stock mounting bolts so all they would have to do is unplug the bad and plug in the good.

Hope this helps!

P.S. This ignition system grounds through the advance/pickup plate then through the distributor base. Sometimes this is iffy. The black wire in the three wire harness going into the distributor is the ground wire. I would splice in a length of black wire and with an eyelet on the other end, ground it direct to a clean rust and paint free spot on the block. A good spot is the 3/8" bolt that holds on the coil bracket. It's close to the distributor.
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Old 02-27-2019, 01:30 PM   #5 (permalink)
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Quote:
Originally Posted by Marty, SoCal View Post
"...she will not restart sound like no spark when I crank the engine over it spins but no fire except when I release the key I get a slight sound like she wants to fire but only when I release the key..."

This is the classic symptom of a dead Motorcraft ignition module. 10 minutes running then stall. Spark on key release.

These modules are a high failure rate item. The genuine Jeep/ Motorcraft ones are better than the others if they are still available. Avoid chi-com made ones if at all possible. Should have a blue strain relief where the wires go into the module.

I would find and keep a good spare in your glove box. Some of my customers stacked them using threaded rod instead of the stock mounting bolts so all they would have to do is unplug the bad and plug in the good.

Hope this helps!


This ignition system grounds through the advance/pickup plate then through the distributor base. Sometimes this is iffy. The black wire in the three wire harness going into the distributor is the ground wire. I would splice in a length of black wire and with an eyelet on the other end, ground it direct to a clean rust and paint free spot on the block. A good spot is the 3/8" bolt that holds on the coil bracket. It's close to the distributor.
that is the one part of the ignition system I have not replaced. and for a vacuum leak. how to find a vacuum leak do I spray carb cleaner around all the vacuum line and it should change the idle speed. I this a correct way to find a leak. I also have a 99 F350 v10 throwing a code stating a possible vac leak so I need to find the leak on the beast. thank you for the advice.
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Old 02-27-2019, 01:31 PM   #6 (permalink)
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Originally Posted by total newb View Post
Thermo switch controled vacum leak*
never heard of this part can you elaborate please? location and what it looks like?

Last edited by Jokerrw4; 02-27-2019 at 01:35 PM.
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Old 02-28-2019, 08:13 AM   #7 (permalink)
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I've had a new coil do this and a condenser do this. They work until they get hot.
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Old 02-28-2019, 12:35 PM   #8 (permalink)
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Check out some of the info on here.

Berkeley's Full-Size Jeep Grand Wagoneer SJ Information

The thermos switch is usually a 2-4 port vacuum switch. And as it warms up becasue the switch allows vacuum thru different ports you could have a vacuum leak.

To find a vacuum leak you can use carb cleaner and spray it around areas you think it is leaking. If the RPM's go up you have a leak.

But I agree with Marty as that ignition control unit was always a problem with the older Jeeps. There are many ways to remove it completely which is the best option.
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Old 03-04-2019, 07:18 PM   #9 (permalink)
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Quote:
Originally Posted by madcratebuilder View Post
I've had a new coil do this and a condenser do this. They work until they get hot.
I have replaced the coil but there was no condenser

Quote:
Originally Posted by Marty, SoCal View Post
"...she will not restart sound like no spark when I crank the engine over it spins but no fire except when I release the key I get a slight sound like she wants to fire but only when I release the key..."

This is the classic symptom of a dead Motorcraft ignition module. 10 minutes running then stall. Spark on key release.

These modules are a high failure rate item. The genuine Jeep/ Motorcraft ones are better than the others if they are still available. Avoid chi-com made ones if at all possible. Should have a blue strain relief where the wires go into the module.

I would find and keep a good spare in your glove box. Some of my customers stacked them using threaded rod instead of the stock mounting bolts so all they would have to do is unplug the bad and plug in the good.

Hope this helps!

P.S. This ignition system grounds through the advance/pickup plate then through the distributor base. Sometimes this is iffy. The black wire in the three wire harness going into the distributor is the ground wire. I would splice in a length of black wire and with an eyelet on the other end, ground it direct to a clean rust and paint free spot on the block. A good spot is the 3/8" bolt that holds on the coil bracket. It's close to the distributor.
well I changed the module and added the extra ground wire to the coil bracket at the block when I tried to start her she would barely start and run worse won't idle, I moved the distributor counter clockwise about 9 degrees idles a little better but hard to start. I forgot to add that I have also replaced the ignition control modular about a month ago.
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Old 03-04-2019, 10:09 PM   #10 (permalink)
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did you change the fuel filter after the problem started?
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Old 03-05-2019, 12:37 PM   #11 (permalink)
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I replaced the filter in the beginning about 4 months ago and only have about 10 hours of run time.

Also after replacing the module and before messing with timing when it ran it sounded like I had a rod knock never heard it before changing the module.

Can someone tell me a good hosting site so I can post a video of it running?

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Old 03-05-2019, 05:46 PM   #12 (permalink)
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Quote:
Originally Posted by Jokerrw4 View Post
I replaced the filter in the beginning about 4 months ago and only have about 10 hours of run time.

Also after replacing the module and before messing with timing when it ran it sounded like I had a rod knock never heard it before changing the module.

Can someone tell me a good hosting site so I can post a video of it running?

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what condition is the fuel tank in? has it been sitting for a long time before you started working on it? rust? water? fuel lines?
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Old 03-06-2019, 10:13 AM   #13 (permalink)
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Yes she has sat for awhile before I got her.

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Old 03-06-2019, 10:25 AM   #14 (permalink)
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what condition is the fuel tank in? has it been sitting for a long time before you started working on it? rust? water? fuel lines?
I have replaced the rubber fuel lines supply and return.
Not the metal lines.
I have not seen any water but how would I look for water? Pull the carb and look in bowl? Filter is metal and has 1 outlet going to carb and 2 on the opposite one is a return and the other is supply so those clear fuel filter won't work. I don't think.
Is the only way to check the fuel tank for water and rust Is to drop it or is there another way?

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Old 03-15-2019, 01:12 PM   #15 (permalink)
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You can pull the carb fuel inlet tube off the carb, insert the line into a dry, clear plastic bottle and crank the engine ( Ignition module disconnected for no spark) and see what the fuel looks like that is getting to the carb. Any water will separate out at the bottom as an easily seen layer.

The top of the Motorcraft 2100 two barrel can be removed while the carb is still on the vehicle, and even ran with the top off if you are careful. You can see into the bowl and look for corrosion and sediment, too.


Another common failure I used to see at the dealer was a blown power valve on the 2100 and 2150 two barrels. All it takes to blow the valve is one backfire.

IIRC, the earlier ones used a separate 1/4" vacuum line off the bottom front of the carb to the back upper intake manifold runner. If the power valve blows, it dumps raw gas into those two cylinders that the runner feeds. The later carb (IIRC) has the power valve vacuum connection internal in the carb, and if blown, will leak raw fuel into all the cylinders. If you remove the vacuum line and/or the cover over the power valve and you find raw fuel in there, the valve is blown.


Top: Power valve cover with internal vacuum.
Bottom: Power valve cover with external vacuum.

Last edited by Marty, SoCal; 03-15-2019 at 01:17 PM.
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Old 03-16-2019, 01:09 PM   #16 (permalink)
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Ok I changed the Ignition Module and added the extra gound wire and I grounded it with the bolt holding the coil bracket. She would not start. I turned the distributor counter clockwise about 10 to 15 degrees it started but would not idle and hard to start I had to increase the RMP's. The rpms would rise then lower and keep going up and down.

I messed with the timing back and forth couldn't get it to idle. then I found a vacuum line disconnected from the front vertical port toward the front center area on the intake manifold.
So I uninstall the new ignition module put the old one back on, I moved the distributor back to the original position. she now restarts but idles rough does not idled like before and then died after running for about 10 minutes, I have not been able to let it run for any length of time I am going to do the checks that Marty SoCal suggested. I am baffled why she would not run right with the new Ignition Module.
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Old 03-16-2019, 10:13 PM   #17 (permalink)
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New doesn't necessarily mean that it's free from defects.

It also could mean that the ignition module wasn't/isn't the problem.
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Old 03-17-2019, 08:04 AM   #18 (permalink)
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Are you setting the timing with a timing light or just winging it???

If you don't own a timing light, you can rent one from the local parts store or static time it by putting the timing mark at 5 degrees advanced before cylinder 1 TDC, turning on the ignition and rotating the distributor until you get a spark from the coil wire. The ignition rotor should be pointed at or a little after the post for plug #1 inside the cap at TDC.

When the engine stalls after 10 minutes and does not restart, does the ignition still spark while cranking???

Both ignition modules should have a blue plastic insulator/strain relief where the wires go into the module. Different color ones are wired differently.
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Old 03-19-2019, 06:54 AM   #19 (permalink)
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You have to determine if it ignition or fuel or air related. Does the choke plate close once warmed up? Is the spark still strong once itís warmed up, are you getting fuel coming out of the Jettís once it warmed up? Start simple. If your gas tank is questionable run it of a can of fresh fuel. I had my distributor go bad on my 77 ram charger and this same issue happened once hot. Iím not saying thatís what it is, you have to rule things out. Find out which element of combustion youíre missing, it only takes three after all.
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Old 04-01-2019, 05:04 PM   #20 (permalink)
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As mentioned before run it out of a separate gas can to make sure it's not running out of fuel from the tank. I had a tractor do that when the tank outlet was plugged. It would drip down and fill the fuel line from the tank to the carb. Then it ran great for about 5-10 min and then would die once the fuel in the line was gone.

You mentioned the fuel filter with the return line going towards the carb. Make sure the return is above the outlet to the carb on the filter.
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