Will idle fine, but die 30 ft up the road, ICM?

[RecluseLoneWolf]

72 CJ5 factory AMC 304 , The jeep has sat for 20 years but I have been working on it for the last couple months and now is basically mechanically restored, it idled fine while the carb and timing was tuned (and a couple more minutes of just listening), but as soon as it left the driveway today it died and wouldnt turn back over. We towed it back and checked a few things like fuel and spark plugs, then it fired right back up and died 30 feet up the road and wouldnt start again.

The coil is the old coil so it should be replaced anyway but is this the issue? Could old coils be intermediate? Now Ive tried researching ICMs, I cant seem to find one like the one on my jeep...





Motorola and single plug 4 wire connector, Can I still find one of these? I dont want to do a crazy upgrade right now, I want the jeep ready for winter right now.

Thanks for any help

 

[DHugg]

I was taught by my Dad to be sure of fuel first, then look to ignition. The MC2100 carb can have the float level set too low, and the engine will starve as RPM demand goes up. On the AMC 304 in my '80 CJ7 , I know the linkage in the accelerator pump is too long, and she stumbles due to fuel starvation during off-idle throttle.

A good carb rebuild will eliminate doubts.

 

[Torxhead]

Upgrading to a better ignition would be a good idea, but I would agree to look at other options first. Like you could check that coil for 1.35 ohms across the positive and negative terminals while also looking at that carb.

 

[RecluseLoneWolf]

I was taught by my Dad to be sure of fuel first, then look to ignition. The MC2100 carb can have the float level set too low, and the engine will starve as RPM demand goes up. On the AMC 304 in my '80 CJ7 , I know the linkage in the accelerator pump is too long, and she stumbles due to fuel starvation during off-idle throttle.

A good carb rebuild will eliminate doubts.

I mention in my first post fuel was checked, also it has new pump, new carb, cleaned or new lines, new filter.

First time it died was in gear but real low rpms, second time was in the revs a little more.

 

[gutthans]

Well, given that you replaced all of those parts...did you drop the fuel tank and check the pickup? Being able to idle and drive off, only to have the motor totally die can be attributed usually to an ignition shutdown, or fuel starvation.

Electronic components either work, or don't...they can be finicky and work cold, but not hot sometimes. But I'd look at a line restriction in the sump of the tank possibly...

 

[RecluseLoneWolf]

Well, given that you replaced all of those parts...did you drop the fuel tank and check the pickup? Being able to idle and drive off, only to have the motor totally die can be attributed usually to an ignition shutdown, or fuel starvation.

Electronic components either work, or don't...they can be finicky and work cold, but not hot sometimes. But I'd look at a line restriction in the sump of the tank possibly...

Yes tank was dropped, cleaned(outside, inside was spotless), treated and painted, pick up and level sender replaced. Weve checked fuel, pulled the line off the carb and cranked the motor and the fuel came out with a lot of force. Took the carb apart and all was good. Took the fuel cap off and tank was not under vacuum.

We are now thinking its getting too much fuel or theres not enough power to ignite it, we'll try a cheap fuel pressure regulator first. If not then a cool high power ignition setup.

Turns out the unit in my pictures is not a ICM, I think its just old enough to not have one, explains why a motorola icm never came up in search.

Thanks for the replies, I guess I just need to keep tinkering with this old girl.

 

[RecluseLoneWolf]

Just for kicks I just went out to see what it took to die in neutral, warmed it up and then held it at about 2 to 2.5 k rpm, and sure enough about 20 seconds later it just died. Just to be clear it will idle and take short revs all day.

Will find a fuel pressure gauge and go from there, will see if the pressure drops or raises when it dies.

 

[Lumpy Grits]

Ck your float level and fuel filter.
LG

 

[RecluseLoneWolf]

Ck your float level and fuel filter.
LG

floats are good, filter is new.

 

[Dan77CJ7]

are you using a fuel pressure regulator? i always ask.....every carb iv had on mine likes 3-3.5 psi.

 

[RecluseLoneWolf]

are you using a fuel pressure regulator? i always ask.....every carb iv had on mine likes 3-3.5 psi.

No but looking for one now actually

 

[GARGOYLEJEEPER]

First not Motorola ICM but voltage regulator for alternator, you say fuel is good, but you need to be looking into carb while running and see why it dies. If no fuel when it dies it is fuel.
Need to hook up light to coil (scope, timing light, meter, test light, etc...) and watch it flash, stops flashing, ignition timing.
Also unplug ambient temp & solenoid vacuum valve during testing to cancel them out of the equation, if still hooked up.
I hope this helps.

 

[Lumpy Grits]

floats are good, filter is new.

How did you confirm this?
Doesn't mean some of the crud you flushed didn't end up in the fuel line and you now have a plug'd filter.
How did you confirm your float setting?
You can take the top off a Carter(and many others)and see the fuel bowl and ck the level that way.
LG

 

[RecluseLoneWolf]

How did you confirm this?
Doesn't mean some of the crud you flushed didn't end up in the fuel line and you now have a plug'd filter.
How did you confirm your float setting?
You can take the top off a Carter(and many others)and see the fuel bowl and ck the level that way.
LG

Took the carb apart, edelbrock, easy. Check everything, blew out everything, the works.

I cleaned everything well, the filter is not going to be restricted with dirt, high fuel pressure is the concern now.

 

[RecluseLoneWolf]

Welp, drove it today, felt good. What was the problem you ask? I dont know why but it was the distributor. I upgraded to HEI since everything else was upgraded, and it didnt die on me.

Thanks for the help again guys

 

[Dan77CJ7]

Right on the HEI really cleans up the place.. and so simple.

 

[Torxhead]

Thanks for the update RecluseLoneWolf, hopefully it was just an ignition problem.