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Electrical Issues!!

6K views 111 replies 13 participants last post by  TexasMan 
#1 ·
Hello Yall,
I've been having some serious issues lately with Bob (1984 CJ-7, with AMC 304 and GM TH400 Auto Tranny).

1- About a month ago, the jeep kept trying to start with no key in the ignition
Solution: I replaced the starter & the starter solenoid...That took care of that issue

2- a week later, I started the jeep, it started with no issues and let it warm up. 5 minutes later the engine shut off on its own. I tried to start it, but it cranked without starting.

3- I added about 5 gallons of Octane 87 (gas for my John deer, and sprayed some starter fluid in the carb. After a few tries the engine started and ran smooth.

4- I shut off the engine, but a few minutes later when I was ready to take off, I couldn't get the jeep started...Sounded like "No Spark" issue to me

5- I replaced the pickup coil inside the distributor, and the jeep started immediately

6- I adjusted the timing (5-7 degrees BTDC) and adjusted the fuel mixture screws until I had about 18 PSI on the vacuum Gage (Motorcraft 2100 2BBL carb)

7- I went for a drive, and the engine ran like hell...coughing, hesitating, and jerking real bad when I pressed the gas peddle, it seemed to run better if I just maintained a steady speed

8- I change the Ignition module, and that reduced all the symptoms above drastically...I thought I was done, and might have been bad gas (the five gallons I added in step 3)

9- I decided to drive the jeep this week in order to burn off the gas I had in the tank and make room for a fresh tank of gas

10- The jeep had a slight cough at lower speeds, but once I got to 45 it seemed normal

11- Coming home from work today, while taking off at a red light the jeep backfired at the carb, but did not die, and seemed fine. I was able to accelerate to about 55...Then with no warning the engine just died!!

12- I tried starting the engine but had no luck and ended up having to toe it home

Note:
I confirmed the battery and alternator were good (Alt: 14.34 while running)

For those who are not familiar with "Bob", it originally came with a151 cubic inch and I ended up installing an AMC 304 and a GM TH400 Turbo from a 1978 jeep CJ-7

I am wondering if I need to take a close look at my distributor and ignition coil...What tests can I run to narrow this issue down

I appreciate any tips
 
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#5 ·
I replaced the ignition coil, but that was a dead end! I am now suspecting fuel delivery issue plus a dirty fuel tank. Even though I replaced the mechanical fuel pump a year ago, I know remember when it happened! I wasdriving home after helping a friend with her car when the jeep quit on me and got me stranded on the side of the road. I called my wife and had her buy me a fuel pump, and that took care of that issue,

After I replaced the coil and failing to start the engine, I sprayed a bunch of starter fluid in the cab and it started real rough for a few seconds then died. I know how to test the fuel pump, so here is the next plan:

1- Drop the gas tank and have it professionally cleaned
2- Test and replace the fuel pump if needed
3- Take the carb apart and clean it

Please let me know if I am missing anything, or if I'm going in the wrong direction

Thank you for your tips
 
#6 ·
When you drop the tank, remove the sending unit and have a good look at the filter screen on the bottom tube. Might be clogged.
Check the sending unit itself to make sure its in good shape while you are there.

Check your fuel filters and replace them. They are cheap so its worth changing them at this time.

Look for vacuum leaks that can cause a very rough idle. A cracked brittle hose or intake gasket????

Finally, clean all contact grounds at frame, alternator, battery, body, coil, etc. It's good to make sure you are well grounded for optimum spark.

Good Luck
 
#7 ·
Thank you so much for the tips "258". Unfortunately I ran out of time today to go through with the plan, but I will try to get to it in the next couple of days after work. I already changed both fuel filters, and man that fuel going into the filter looked brown. I think the former owner may have under estimated how long the jeep sat before I bought it

Thanks again for the tips
 
#8 ·
If the fuel was that brown, you should most definitely pull the sending unit from the tank. That filter at the bottom tube within is probably pretty dirty. The new filters will get clogged quickly otherwise.

Dropping the tank is pretty easy. Just make sure you have less than 1/4 tank of gas to ensure its light in weight. Ask me how I know, lol.

Disconnect the rubber fuel HOSES (Fuel/Vent) from the tank (at tank) and remove that side guard at that location just under rear tire wheel well.

Remove bolts at frame cross member (I believe there are 4) and disconnect the GROUND wire at that cross member top; it grounds the sending unit. (No worries, tank will not drop yet because the 5 front (or rear) bolts are still screwed in)

Now get your hydraulic jack and a 2” x 6” or similar piece of wood for the hydraulic and place it dead center under the tank. Remove the 5 rears bolts and gently drop the tank till you can get to the sending unit. Don't forget to disconnect the wires at UNIT and remember where they go.

No need to remove the tank all the way however, you mentioned you need to clean it out so pull it away from the vehicle. Once you lower it, it will slide right out.

When you remove sending unit, you will be able to view that filter within the gas tank. REPLACE it and if you have a PLASTIC float, get one of those $5 BRASS floats.
Wash the tank out real good and install the sending unit. Use small amount of grease at "O" ring at top of tank to ensure a good seal.

REINSTALL TANK! - (By the way, clean all wire contact points too!)
* IF YOU CAN VISUALIZE EVERYTHING I DESCRIBE, IT WILL TAKE LESS THAN AN HOUR. JUST HAVE ALL YOUR TOOLS READY.
You will never have to worry about bad filters for along while!
 
#9 ·
Update...It is back in one piece!!!

1- I removed the tank and took it to a professional place and had them clean it out ($90)
2- I replaced all the hoses going to the gas tank directly or indirectly
3- I discovered the tank's float was cracked and full of rust...That explained why my gas Gage never worked
4- I replaced the fuel sending unit (Amazon...$50)
5- I pulled the carb and rebuilt it (Carb kit...$45)
6- I readjusted the carb getting maximum possible vacuum (19 PSI)
7- I adjusted the idle (between 750-800 rpm...Automatic transmission)
8- I checked the timing (it is now set at about 8 degrees BTDC)
9- When I tried to start it last night thae battery was dead (87% charged), so I put it on a trickle charge until it was fully charged today about 6:30 pm
10- Took it for a drive...
A- it coughed and sputtered as I started accelerating
B- It seemed to do better at a "Steady speed"
I stopped at a gas station, filled it up, but when I tried to start it, it almost sounded like the battery was discharged...Even though I just took it off the charger at 100% full...It only does that after you shut off the engine then try to start it within a few minutes (never did that before)

Question:
Is it possible that my timing is way off...what timing should an AMC 304/5.0 with an automatic GMC TH400 Turbo auto transmission should be set to? This is the one thing that I am 100% uncertain about. Looking at all the details above...any suggestions?
 
#10 ·
CLEAN your GROUND contacts. (battery terminal, starter cable (at starter), solenoid (fender), alternator, coil (block), etc.
Clean them all and dab some die-electric grease on those contact points when you reinstall. How old is your battery?

A bad ground will cause your engine to struggle to start up and cause lack of power. CLEAN them thoroughly (brass brush, sand paper).
 
#14 ·
YES on the GND issue.
Your NEG(-)battery GND should be attached to the top mounting bolt of the starter motor.
Also-When was the last time you changed the fuel filter and tested the psi of your fuel pump?
Also-What type of connector do you have on the coil. The OEM 'horseshoe' has a long history of contact issues.
LG
 
#15 ·
Thanks a lot for your reply "LumpyGrits", I really appreciate it. Here are the answers to your questions:

1- It has been less than a month since I replaced both fuel filters
2- I replaced the ignition core, ignition module and pickup coil less than a month ago, the core has a four prog electrical plug that has only two active connectors in it, I think it was designed for an 84 bronco

A couple of hours ago, I did the following:
1- Adjusted the timing to 5 degrees BTDC
2- rechecked the idle mixture screws
3- Adjusted the idle speed
4- Cleaned all cables from starter to battery and engine block

Took it for a test drive, it seemed a little better, but it still hesitated at startup and felt sluggish until I hit 45MPH, then it seemed to open up better.

Vacuum leaks next!!!
 
#16 ·
A new gas filter does not always mean it is filtering after a few miles if you have trash in the gas tank. Take your filter off and cut it open to see if it is clogged. If it is it is doing its job.

If your Jeep sat for a while with very little gas in the tank this could be an indication of water in the gas if the gas was not an ethanol blend--the ethanol will suspend the water. On the other hand ethanol will leave a residue and will clog a fuel filter very quickly. Sea Foam or MMO added to a full tank of gas will help, but you will probably have to filter it out or clean your tank.

I had this problem with my RV. I'd be driving along and it would loose power on hills, then would start backfiring and then lost power all together. I'd let it sit for several months with an almost empty tank--just forgot to fill it up at the end of the camping season. For some reason GM decided the in-carb filter the size of my little finger was adequate filtration. Added a "see through" filter and had to change it the first time after 300 miles. Took three changes before it stopped filling up. If this hadn't worked I would have had to drop an 80 gallon tank to clean it out.

You may just have trash from the pump in your tank so your best bet would be to drop the tank and do it right even if it is the hard way.
 
#17 ·
Have you ruled out the "EGR" valve.
Remove it and clean the port if it's covered with carbon deposit. Be careful not to rip the gasket.
Try not to spray the diaphragm with carb cleaner but scrape it and work it FREE.
A failing "EGR" will cause rough idle when cold. Then check and look for vacuum leaks.
 
#18 ·
Thank you for the tip "258", the EGR valve is less than one year old, but I'll recheck it again. I drove the jeep yesterday after I adjusted the timing back to 5 degrees...Man, it never ran worse!! I thought it was going to give out on me on the way to work, then I had a thrill ride on the way back home...I had the worst ride. More sputtering and hesitation than ever before!. This morning I started up and sprayed Starter Fluid around the intake gasket, but did not sense any leaks (RPM did not change), so this weekend I'll check every vacuum hose.
This really blows, because it is the best time in Florida to be in a jeep, but I cannot trust it in heavy traffic the way it is driving right now!

I'll report back on Saturday!
 
#20 ·
Thanks for your Tip Bob. I already dropped the tank 2 weeks ago and had it professionally cleaned, I can tell you with 100% certainty the tank is not the problem. Tomorrow, I am going to trace every vacuum hose on the jeep and replace it if I have the slightest suspicion that it needs to be replaced. The fuel pump has less than 8000 miles on it since I replaced it a couple of years ago, but you know it was about $30, so it'll be no big deal replacing!

I'll report tomorrow with my findings
 
#22 ·
Update...
1- I removed the EGR valve, cleaned it off and made sure it was not sticking...It is about one year old
2- I checked all vacuum hoses and plugs and made sure all was good
3- I found a significant leak from the cap of the charcoal canister on the driver side, I fixed the leak.
4- I readjusted the timing to 5 degrees BTDC
5- I readjusted the idle Mixture screws and made sure they bot were turned out the same exact # of turns which gave me 18 PSI on the vacuum Gage

With all of the above...Still running horrible! Sputtering and coughing at take off up to 45 mph when it starts running better, but never really ran good, it is still not road worthy!

This is the sort of thing that happens when you yank a 151 CID and swap it with a 304 CID with a different wiring harness...I am really not sure where to go from here!

This is what I'm certain about:

1- The gas tank is clean
2- The fuel filters are clean
3- The Ignition Coil is new
4- The ignition Modual is new
5- The pickup coil is new
6- The car was rebuilt last weekend
7- The timing is at 5 Degrees BTDC
8-The starter and starter Solenoid are new
9- All vacuum hoses and plugs are good
10-I sprayed Starter fluid around the intake, but did not notice a change in the RPM

What am I missing?
 
#23 ·
For any engine to run correctly you need fuel, fire, and air. Looks like you've covered the first two so have you checked your air cleaner/breather?

Starting fluid has ether in it so it is evaporates quickly and the fumes are extremely flammable. Next time use WD40. In a pinch you can use it as starting fluid.
 
#25 ·
Thank you gentlemen, for your replies:

Air cleaner: I recently installed one of them K&N filters, the one you clean and reuse...It was one of the first things I checked, it looked very clean
Spark Plugs: I removed the spark plugs (less than 8K miles on them), inspected, cleaned and regapped them to .35. from the carbon residue, the engine seemed to be running a little on the rich side, but not too bad. The spark plugs are brand new within the last few months (I bought the nice 8.0 ones. I have not rechecked the fuel filters after I cleaned the tank, but I will. To be totally on the safe side I will replace all the spark plugs...Speaking of which .35 is the correct gap for the AMC304...Correct?
 
#26 ·
Could someone tell what this part is (bicture at the bottom)? It has a vacuum hose on one end, and electric plug on the other end. It is located at the right (passenger) rear corner of the intake...currently not connected

Also: How do I check that the "Throttle positioning Assembly" is adjust and working properly (first picture
The last two pictures are what was originally connected when I has the 151 CID engine in it, I was told I did not need these connected for the AMC304, is that correct? The engine was running fine (with slight hesitation at initial take off) with hoses disconnected as they show before I started having my recent issues!
 

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