88 GW dies when it gets hot

[mgmann]

We?ve had some hot weather here in Montana lately and two days ago my 88 GW started stalling when hot. I can drive it 8 or 10 miles and it acts normally then all of a sudden it dies and won?t start again until it cools off. I tried putting a little fuel into the carburetor to see if maybe it wasn?t getting any gas and that makes no difference. After a few hours when it?s cooled off it fires right up.

Any thoughts? Ignition module?

[4x4Dad]

Ignition module? If you have a spare as most of us do, swap it out next time it stalls.

[joe]

If it's a stumble free like you turned the key off, likely the ign module. If it's a surging stumble as it shuts down maybe vapor lock?

[mgmann]

No Luck!

Installed my spare ignition module and even swapped coils. No luck.

Yesterday drove it about 10 miles before it died. Went back out to get it this morning and it fired right up and ran like a champ. Raced for home at break neck speed then let it idle until it died. Doesn't seem to have any spark.

If the problem were vapor lock wouldn't it fire if I put a little gas in the carb?

Any suggestions on where to go from here would be greately appreciated.

[aerocorey]

Cam sensor. It could be right on the edge of being bad. Electrical resistance goes up when temperature goes up, so it works when it's cold and doesn't when it's hot.

It's a big issue with early XJ crank sensors. Maybe you're having a similar issue?

[FSJ Guy]

Cam sensor. It could be right on the edge of being bad. Electrical resistance goes up when temperature goes up, so it works when it's cold and doesn't when it's hot.

It's a big issue with early XJ crank sensors. Maybe you're having a similar issue?

No cam sensor in a stock 88 FSJ. It should have a V8 AMC 360. Very different from an XJ.

X2 on checking the ignition module. If that checks out OK (ie, it still doesn't start with a different module), try replacing the pickup module inside the distributor. You can replace it without removing the distributor.

[aerocorey]

...try replacing the pickup module inside the distributor. You can replace it without removing the distributor.

How is this not a cam sensor?

Installed my spare ignition module and even swapped coils. No luck.

OP already tried a spare module. Call it a pickup module, a cam sensor, a hall effect sensor...whatever you want to call it, it just tells the computer where the cam is. I referenced the XJ crank sensor issue just as an anology to illustrate the nature of sensors (and also because I've burned 3 crank sensors on MJs over the years). mgmann, if you do some searching you can prolly find specs on the pickup module and check it for proper resistance.

[serehill]

LMAO

[mgmann]

Removing trigger wheel?????

Got a new pickup coil at a pretty cheap price. The manual says to use a small gear puller to remove the trigger wheel. Nowhere in the town where I live can I find a small gear puller. Any other way to remove the wheel and if not who sells a small puller that will work?

[babywag]

I've always just used 2 flat screwdrivers.
Be mindful of the little roll pin have a magnet handy.
They come right off w/ a little pressure.

[4x4Dad]

Ditto on the flat screwdrivers. The two biggest you have that will fit under it, 180° apart. First time I did it, I lost the pin babywag mentioned. A section of coat hanger wire worked, but not recommended as a permanent solution.

[FSJ Guy]

Oops. Sorry. I missed that the OP tried replacing the module already.

Not trying to pick a fight on the internet, but I've never heard the distributor pickup called a cam sensor. <shrug>

Cam sensors are for those new fangled multiport FI engines. :-p

[aerocorey]

Eeh...my bad, I just read that again and I came off a Lil harsh. Didn't seem like that in my head when I typed it.

Cam sensors in more modern ignition systems with distributers sit in the same place as ours and do the same job. It's all semantics.

OP, how's it coming?

[FSJunkie]

Cam sensors on the newer Jeep 2.5, 4.0, 5.2, 5.9, and probably a few others were inside the distributor, under the rotor, and read the on-off pules from a one-bladed reluctor ring to tell the ECM when to fire which spark plug and fuel injector.

FSJ's have a sensor in the same place on an 8-bladed reluctor ring to tell the (primitive) ECM when to fire which spark plug. It serves a very similar purpose.

The difference is the distributor on newer engines is locked into place, so the distributor position correlates directly to camshaft position, hence why the sensor in the distributor is called the camshaft position sensor. On our FSJ engines, the distributor can be rotated independently of the camshaft, so the distributor sensor has no correlation to camshaft position. It is merely a distributor position sensor, pickup coil, trigger coil, whatever you want to call it.

[mgmann]

Trigger wheel slot - which one or does it matter?

Well, couldn't get the trigger wheel off without removing the distributor. No biggie, have done it many times. Didn't turn the engine while it was out, so everything should have lined up perfect. Just can't seem to get it timed right. When I put the trigger wheel back on I noticed that it has two slots for the pin. They seem to be on exact opposite sides of the wheel, so I didn't think it mattered which one I used. I tried to use the one that was used originally, but not sure.

Please don't tell me it matters which slot is used to line up the wheel!

BTW - thanks for all the help. Notice your list of vehicles - first car I ever had was a 64 rambler. Not too impressive, but a station wagon with lots of room when the rear seat was folded down