Still having Problems with My m38

Bill_F · Post by **Bill_F** » Mon Jul 02, 2012 8:01 pm

Ok I thought I had my jeep fixed. Seems my ignition switch was faulty causing some of my problems. I changed it out for a keyed civvy switch that just has on and off. Ran fine all weekend. It did spit and sputter when going down hill with my foot off the gas but it has always done that.

The new problem. I drove it about 12 miles tonight to get ice cream, ran fine all the way. Was at the place probably a half hour. I started it and the idle was a little rough hit the gas and it would smooth out. Pulled out onto the main road was shifting into 2nd and the engine died put quickly restarted it self, it did this two more times until it reached operating temp then is was fine all the way home. When I pulled it into its parking space it was idling rough again. Turned it off and went inside. About an hour later I took it to run an errand about a mile from my house. It did the same thing again. I stopped at the store, picked up what I needed went back out to the jeep and it ran fine on the mile drive home, idle however was rough again when I went to park it.

I have replaced the points, condenser, and coil. I triple checked that I had the points adjusted correctly.

My ideas what could be wrong let me know what you think.

1) Plugged fuel filter
2) Fouled plugs
3) Bad coil
4) Valves out of adjustment (they don't seem to be making any more noise then when I first rebuilt the jeep)
5) Something with the carb
6) something with the fuel pump
7) ??????

Just shoot the thing and bury it in an unmarked grave

DJ · Post by DJ » Mon Jul 02, 2012 9:14 pm

Don't shoot it. We all run and idle poorly on occasion. Do some methodic trouble shooting . If you are sure the electrical is good ,then check fuel delivery. Is your air filter operating properly? Heat riser sticking?

Bill_F · Post by **Bill_F** » Tue Jul 03, 2012 4:29 am

It will run and start fine. The problem seems to happen when I hit the gas to accelerate. The engine just dies like you hit the ignition switch, however it quickly restarts itself while moving down the road if you dont press in the clutch. It idles rough after you take it for a trip.

oilleaker1 · Post by **oilleaker1** » Tue Jul 03, 2012 6:38 am

If it was mine, I'd check for vacuum leaks at the carburator base, and do a quick float bowl cleanup and blow out the idle circuit. Then adjust the valves. I,ve had the put put and poor idle like you and it was a combination of idle mixture and tight valve settings. You can play with the timing a little and then test drive over the same stretch of road or hill and compare. The better setting will show in performance. Be careful when you get it right, the acceleration might strain your neck

. John

Bill_F · Post by **Bill_F** » Tue Jul 03, 2012 6:52 am

Started it this morning before work and the idle was very rough, it did start easy but ran rough. I didn't have time to test drive it or let it warm up.

Post by **wesk** » Tue Jul 03, 2012 9:05 am

A stumble and stall off idle is normally an accelerator pump issue. Before shot gunning the entire jeep powerplant and making assumptions that something recently changed was a good part or a recent adjustment was a good adjustment it is always best to use the troubleshooting guide in your manual. TM 9-8012 Page 77 Par g is a good starting place.

I would not be surprised to see a deteriorated accelerator pump diaphragm. Which by the way is a simple 5 minute check.

Bill_F · Post by **Bill_F** » Tue Jul 03, 2012 10:47 am

I am going to check the carb tonight. I did check the trouble shooting list in the manual and thats how I came up with my list of could be problems.

Bill_F · Post by **Bill_F** » Tue Jul 03, 2012 4:41 pm

Ok took the carb off tonight. Took it apart and did find some dirt in it. Cleaned everything up and put it back together. I then put it on the jeep. I have an inline filter after the pump and before the carb. It was a metal one. I changed it for a plastic one so I could see inside of it. Started the jeep, it started well and did idle better, got out of it and it the throttle by hand it stumbled. Looked at the filter and it had hardly had fuel in it. When I hit the throttle is basically drained the filter and you could see air moving to the line to the carb. Very little fuel was coming from the pump it was just a small dribble. I am not leaning towards my fuel pump. I do not have a way to test pressure right now.

Bill_F · Post by **Bill_F** » Tue Jul 03, 2012 9:19 pm

Ok so I test drove it tonight and it ran fine. Maybe the fuel has always pumped this way but I didnt have a clear filter to see it. I still dont think I can trust it for the over 100 miles I planned on driving it tomorrow. It is getting air from somewhere however as lots of bubble come into the filter. I checked all the fittings and they seem to be tight.

OKCM38CDN · Post by **OKCM38CDN** » Wed Jul 04, 2012 7:03 am

Bill, take the fuel cap off... if it pumps fuel fine then you have a fuel tank vent problem... if that does not work then take a low pressure air (5-10 psi) and insert it into the fuel system starting at the filter working backwards... get a spray bottle filled with soapy water and spray your lines looking for leaks (Bubbles)...

This is how one checks for leaks in a gas line...

I realize the fue pump will not pass the air pushing to the tank but you can work around it... this will be easier than pulling all the lines...

Hope this helps...

Bill_F · Post by **Bill_F** » Wed Jul 04, 2012 7:10 am

I put gas in the tank and everything seems to be better. It was a low but not terribly low.

RickC · Post by **RickC** » Wed Jul 04, 2012 8:09 am

Bill, do you have the original fuel filter in the tank? On my M37 the lower part of filter was gummed up and truck wouldnt run well below 1/4 tank

Bill_F · Post by **Bill_F** » Wed Jul 04, 2012 9:40 pm

I took the fuel pump apart tonight after I drove over 100 miles today. It was skipping some and not keeping the filter full. The pump has a lot of crud it it. I do not have the stock filter on the jeep.

Bill_F · Post by **Bill_F** » Sun Jul 08, 2012 6:26 pm

It looks like I have everything fixed. From the looks of things it was many problems that all hit me at once

1) it was overcharging, cooked a battery and a coil---fixed with new regulator
2) Not wanting to start no spark---fixed with new coil, points, and condenser
3) Would cut out while running, this one had me stumped for the longest time--fixed with new ignition switch
4) Rough idle--fixed by cleaning carb
5) Not getting enough fuel--Fixed by changing fuel pump and finding that the line inside of the tank was not sealing to the cover

Also doing a little PM while I was working on everything else found a wheel bearing a little loose. Took it apart, repacked the bearings, put it back together and she is all set.

Right now she is running as good as ever.

wilfreeman · Post by **wilfreeman** » Wed Jul 25, 2012 10:58 am

Thanks for sharing your findings Bill! All too often, after the problem is fixed, the originator of the post doesn't follow up with his findings (or fixes) - which doesn't help anyone. I am also guilty of this, so I am not really preaching to the choir!

I am having a similar problem at the moment, so this post has given me a lot of areas to check. My problem is that she runs great on my "outings", but when I get back to the shop and let her idle for 5 or so minutes, she will die on me - and sometimes won't start back up until the next day.

- I pulled the air horn off of the carb yesterday - the float was setat about 3/8", so I adjusted it to 9/64". I blew out all the passages that I could get to. I pulled the metering rod cap - the metering rod was stuck! I twisted it with some channel locks and pulled it out, cleaned it up and put it back in after rodding out the jet with a piece of wire. The pump diaphragm was fine. I put it back together and cleaned out the idle screw hole and cleaned the screw.
- I cleaned and gapped the plugs.
- I checked the dist. cap, rotor and point gap.
- I checked the vacuum, but I only have 10# - isn't it supposed to be around 19#? I checked it at the manifold, below the carb. I am going to adjust the timing this afternoon to try to get that up a little.

Ran a lot better - my little "miss" at idle was finally gone too. Had a good bit more power on the road - got her up to 52mph pretty quick! Idle is great!

2 things I did troubleshoot when it cut off the last time yesterday was I pulled the gas line at the carb and turned her over with the ignition switch off - no gas came out. But, I hooked it back up, turned the switch on and she fired up with a little persuasion. I took the gas cap off and ran up the driveway and back - she still cut odd after idling about 5 minutes. The fuel pump was replaced with a civvy unit late last year.

Today, I am planning on doing the following:

- Blow the fuel line out, back to the tank. (It has a new tank, I cleaned the pickup strainer, new lines, new pump and a clear filter after the pump)
- Adjust the timing until I get maximum vacuum
- check the coil (overheating maybe?)

How do I check the fuel pressure? I have a pressure/vac gauge, but how do I hook it up?

Thanks for the info/ideas guys!