Crankshaft Position Sensor

[FJ4013]

Rig: 1978 FJ40 2F

For a year now I have been chasing down an engine shut off issue. It's been mentioned quite a bit on these forums and I have done everything conceivable to correct the issue, however, it still persists.

Reading another 4x4 forum a member had the same issue as I, however, he was driving a newer model 89' Jeep. Another member told him to check his crankshaft position sensor and sure enough that was the culprit.

His symptoms were the same as mine. After 30 ish minutes of driving around the engine warms up and then shuts off. We have to pull over and let the engine cool down before it will start back up. Turns out it was his crankshaft position sensor.

What would the equivalent issue be in the 2F since it doesn't have a crankshaft position sensor? Something is shutting down the engine at normal operating temperature. I check for spark and fuel and have both. Only when the engine cools a bit (10 mins) will it start back up. I've literally done 7 different things based on suggestions by members here and the problem still persists which is why I posed this question relative to the crankshaft position sensor of new model engines.

UPDATE: Culprit may have been a malfunctioning electric fuel pump. It would work at times and then when it heated up the theory is it would quit working altogether or only work intermittently. We replaced it with a stock mechanical fuel pump. Will update in a few days.

 

[thebigredrocker]

Did some searching, I don’t see that it has been mentioned. Did learn there is a 4th gear sensor. Thread below

Transmission sensor (?) 77 fj40

 

[spotcruiser]

NO.

 

[reddingcruiser]

No x2.

 

[Tancruiser]

It was 1978 what’s a crank sensor I’ve heard rumors about this new fangeled think called fuel injection .

 

[cwwfj60]

 

[unklwedy]

What is a carburetor ?

 

[Tancruiser]

There kind of like ignition points

 

[Living in the Past]

There a mark on the crankshaft gear on the front that needs to be aligned with the mark the cam gear. On the flywheel there is a BB used to time the spark from the distributor. You see that in a opening in the bellhousing above the starter. That is as high tech as these old engines get.

 

[emac]

I promise I am not trying to sound like a broken record or being a jerk....but you have posted this problem in two threads and I have offered some very good advice. Please get a spark plug checker (link below) install it and make sure it works when starting the engine. Remove it. Go and drive the car until it quits, put in the tester and see if you have spark. If you do not, then you have an ignition issue. Trace back from plug to dizzy, then to coil to find where the issue is.

If you have spark, then you have ruled out a lot of stuff, like crank sensor (that you dont have). Then go to fuel.

Advance Auto Parts - Down for Maintenance

 

[FJ4013]

I promise I am not trying to sound like a broken record or being a jerk....but you have posted this problem in two threads and I have offered some very good advice. Please get a spark plug checker (link below) install it and make sure it works when starting the engine. Remove it. Go and drive the car until it quits, put in the tester and see if you have spark. If you do not, then you have an ignition issue. Trace back from plug to dizzy, then to coil to find where the issue is.

If you have spark, then you have ruled out a lot of stuff, like crank sensor (that you dont have). Then go to fuel.

Advance Auto Parts - Down for Maintenance

Yes, and I've done everything you've suggested as well as what others have suggested. I have spark and fuel when the shut down occurs. It just has to sit for 10 mins or so and it will start back up. Thanks for the advice in lieu of the smart ass comments from some of the other members above. If everyone here were experts iH8Mud wouldn't exist and thankfully it does.

 

[Tancruiser]

Does your cruiser have points or electronic ignition , maybe the problem is with the coil next time it acts up touch the coil to see if it’s getting hot . Get yourself a Haynes manual and study it and you’ll figure it out.

 

[emac]

Once you figure out that you are not getting spark, post up pictures of your setup. Dizzy, coil and wiring. That will help us troubleshoot where the problem is.

If you are getting good spark, then we can go to fuel supply. Help us help you.

 

[DylanZ]

The same thing happened to me, turned out to be a rusty fuel tank and a faulty fuel pump. Check these... I had to wait for a long after shutting off to allow the "dust" like rust to be settled enough to restart. I changed all my lines and all filters and found all the culprits. Had no issues since.

 

[FJ4013]

Does your cruiser have points or electronic ignition , maybe the problem is with the coil next time it acts up touch the coil to see if it’s getting hot . Get yourself a Haynes manual and study it and you’ll figure it out.

Here is what I have done the past year chasing this problem:

- replaced dizzy with OEM non US dizzy and upgraded to electronic ignition (Pertronix)
- replaced coil with OEM coil AND swapped out with Pertronix Flame Thrower coil to make sure OEM coil was not bad - still had shut down
- replaced fuel pump with slightly higher performance fuel pump and relocated fuel pump to bottom of rig near the gas tank
- added second fuel filter after the fuel pump at pump level to make sure gas is extra clean
- scoped the gas tank to make sure no debris or rust inside. None that you could see aside from some small spots but they were not flaking
- tuned carb (Weber 38/38)
- replaced spark plugs
- wrapped fuel line with reflective heat wrap where it runs over the header (ceramic) into the carb to abate heat in the event of vapor lock
- replaced gas cap
- replaced thermostat
- replaced voltage regulator
- tested alternator - it is fine
- new battery was needed so I replaced that as well

Rig starts up on first turn every time, never runs hot (needle is just above the C on the temp gauge). Runs and drives fine for about 30 minutes then it starts to buck like it is getting too much fuel or not enough fuel and then it sputters and dies. I pull over and lift the hood to let it cool. During this dead time the engine will try to turn over but it won't so I let it cool for about 10-15 minutes and then it will start back up and run fine until it shuts off again after another 15-20 minutes.

I had always thought it was vapor lock but doesn't seem to be the case. I have done everything everyone here has recommended and still the problem persists. I have one guy at one shop telling me its vapor lock and I need to wrap the headers. I have another guy at another shop telling me its not vapor lock but doesn't know what the issue is.

There was a recommendation from a member a few months back recommending it might be a bad ignition switch. I have no idea how to bypass my ignition switch to see if that is the issue.

Bought a Haynes manual and a 2F engine repair manual a year ago and went through most of what was recommended that made sense relative to my problem but still no solutions.

 

[Travis 76]

Maybe the heat is causing you to lose the ground connection to your engine. I had to run a separate ground wire from my battery to the engine block. I attached it to one of the engine lifter bolts at the alternator bracket. Before I did that it had major starting problems, slow labored cranking. I also melted one of my alternator wires from this as the starter was trying to ground through the small alternator ground wire.
Even without running your engine should crank just like it does when you first start up.

 

[S4Cruiser]

Why are you not running a mechanical stock fuel pump?

Definitely odd the engine tries but won't turn over during the dead time you referred to. I'd replace starter (60 series unit) and ignition switch components / wiring.

 

[emac]

So, when it quits the starter is NOT turning the engine over very strong?

 

[FJ4013]

So, when it quits the starter is NOT turning the engine over very strong?

Correct. At first it is somewhat sluggish. Wrrr.....wrrrr.....wrr.... I wait 10ish minutes for things to cool off then it turns over strong and just fine.

Are you thinking I should replace the starter? That it might be heat soak? I live in Florida and it is hot hot hot most of the year here. What about a heat shield? Ever heard of anyone installing a heat shield to shield the starter?

 

[emac]

You have to figure out why it is not turning over fast when hot. Is it lack of voltage or is the starter bad. I guess it is possible that the starter has an issue where it gets hot shorts out and you lose electrical power. When it quits, do other electrical things work? headlights, wipers, heater fan, etc. Is the starter hot as crap when it quits? Check electrical connections at starter, power ground and the little spade connector.

Other possible issue is the engine gets hot and somethings binds. But, if it was fuel or ignition the motor should still turn over just fine. Need to find out why it doesnt turn over when hot.