HEI gremlin

[FJcovet]

I Purchased a partially complete frame off restomod from a fellow mud member last winter and have been chasing what I believe to be an ignition gremlin ever since. I have a 1970 fj40 with a 1976 2f that came with a DUI HEI dizzy. I could get it to start but it had a rough idle so much so that the mechanical advance would kick on and off and made it impossible to time properly. After replacing the cap, rotor, wires, coil, and ignition module there was little change. I then pulled the dizzy and replaced the pickup coil. When doing so I noticed I had about 3/32 gap between the cam gear and the dizzy shaft housing. I added the shims I had, but I still need more to get to the 0.01" spec but it was a lot closer.

This made a big difference. The idle smoothed right out and I was able to set the timing, adjust idle speed, then use the lean drop method to adjust the trolhole carb. I got in and was excited to take my first drive with a properly tuned engine. Wrong! I didn't even get out of my driveway and I noticed the engine stumbling with even very little acceleration. I also noticed when i put my hand in front of the tail pipe, that the exhaust pressure seemed weak. No good puffs of exhaust like before.

Since then I have verified that the dizzy was installed properly. I also purchased an adjustable spark tester. All cylinders jump a gap of 20 which I think means 20K volts. What I thought was weird was that there seemed to be almost a continuous stream of sparks, way more than I though there should be for a truck idling at 660rpm. Sparks would jump a gap of 25 most of the time, and I got no spark at a gap of 30.

During this test I noticed that with one spark plug wire disconnected, I got good exhaust pressure back from what seemed like one cylinder and occasionally a second cylinder would kick in then right back out.

At this point I don't know what to test next. Anyone seen symptoms like this before?

 

[msapers]

Ok, let's start at the beginning.

Make sure (using a voltmeter) that you have a full 12 volts going to your distributor. It's best to run a relay straight off the battery using the original ignition wire to trigger the relay.

Gap your plugs at .040 to start. This is a reletively small gap for an HEI and if you can't jump that gap you've got problems with your system. I run .055 in both of mine.

Make sure your firing order is correct. 1-5-3-6-2-4 You may want to pull the plug in the number one cylinder, turn the engine over by hand with your finger in the plug hole until you feel compression, then remove the distributor cap and make sure that the rotor is pointing to the terminal for the number one cylinder's plug wire.

Did you time the engine with a timing light? 2F's don't time well by ear.

Check your plug wires. Did you switch to HEI specific wires? Are they in good condition? Go outside at night, start it up and have a look under the hood. If you see arcing, it's bad news.

Now, your advance issue - Are you sure that your vaccuum advance is hooked up to ported vaccum? The vaccum line needs to connect to a port ABOVE the throttle butterfly.

When you installed the carb, did you check everywhere to make sure you don't have any vaccuum leaks?

Have you performed a compression check on this engine?

Is the exhaust obstructed/crushed anywhere?

It sounds like you have more than one issue going on but We'll work you through it.

 

[lcwizard]

Unfortunately I had a DUI I purchased new that had the same issues. It wasn't one thing wrong but a whole list. It arrived new with a dead pickup. I replaced that, it started and idled smooth. As soon as I
throttled it up it it began to miss and when throttled down would no longer idle. I replaced the coil just in case. Same thing, started fine , idled smooth but reacted to rpm the same way. I started inspecting things. I noticed that there was extensive galling on the underside of the cap from what looked like contact with the rotor or some other spinning components. I called DUI and they confirmed that a batch of their rotors were out of spec so their solution was to sit some kid down with a die grinder and hog out the plastic until he thought it was good. Nice solution for a 50 cent part on a $350.00 performance item.
I replaced the cap with an autozone item. Huge difference. Ran through full rpms fine. Then about 15 minutes into tuning it developed a miss again. Took it apart again and started looking around and noticed one weight laying over the top of the other. I removed the dist, held it in my hand and spun it with the cap off. The weights were bushed so sloppy they flopped around and would settle on each other.
Back to autozone where I picked up an HEI tune up kit with weights, springs and bushings. I robbed the bushings from the kit and reassembled the dist. This time I installed e-clips at the top of the weight posts. Again, I called DUI and asked why the retaining e-clips were left out. Their reply was they found them unnecessary. The posts are machined for them so I installed the clips anyway as all GM units would have. It's now run perfect for two years. That was my third and last DUI. If I'm going to buy cheap Chinese knock offs I just buy the same off EBAY for much cheaper. If you're looking to go electronic, swap out from a 60 series

 

[FJcovet]

Thanks for the reply. I will try to work through each question.

Make sure (using a voltmeter) that you have a full 12 volts going to your distributor. It's best to run a relay straight off the battery using the original ignition wire to trigger the relay.

I took my battery to batteries plus and had it load tested. The tech said the battery was great. I then used my volt meter and tested from the positive terminal on my 30 amp relay to ground and had 12.8 volts. Just to be sure I jumpered the relay with a fused test wire directly from the battery to the distributor. no change in engine performance.

Gap your plugs at .040 to start. This is a reletively small gap for an HEI and if you can't jump that gap you've got problems with your system. I run .055 in both of mine.

When I replaced the spark plugs, I think i gapped them at either .035 or .040. I knew I had spark issues and didn't want to go to .055

Make sure your firing order is correct. 1-5-3-6-2-4 You may want to pull the plug in the number one cylinder, turn the engine over by hand with your finger in the plug hole until you feel compression, then remove the distributor cap and make sure that the rotor is pointing to the terminal for the number one cylinder's plug wire.

I did something similar. I turned the engine over with the jack crank out of my 03 tundra (It fits right in the crankshaft pulley nut that has the one direction flanges on it) until the bb was lined up in the timing window and both the intake and exhaust valves were closed. I pulled the distributor cap to make sure the rotor was lined up with number 1 cylinder. It was. The wires follow 153624 going clockwise. (see pic)

Did you time the engine with a timing light? 2F's don't time well by ear.

timed with a sears timing light with advance on readout at 0.0 and the bb at the bottom of the window (slightly advanced).

Check your plug wires. Did you switch to HEI specific wires? Are they in good condition? Go outside at night, start it up and have a look under the hood. If you see arcing, it's bad news.

I replaced the wires when I couldn't get it to work. Napa premium. I guess I don't know if they are HEI specific. I was working last night and didn't see stray sparks but I wasn't really looking for them either. I will check it out.

Now, your advance issue - Are you sure that your vaccuum advance is hooked up to ported vaccum? The vaccum line needs to connect to a port ABOVE the throttle butterfly.

Mechanical advance only on my dizzy.

When you installed the carb, did you check everywhere to make sure you don't have any vaccuum leaks?

the PO installed the carb. I have checked for vaccuum leaks, but now that you mention it, that was before I had a good idle so I couldn't identify an RPM change. I will check again.

Have you performed a compression check on this engine?

#1 125
#2 120
#3 115
#4 127
#5 126
#6 124

Is the exhaust obstructed/crushed anywhere?

I don't see any damage, most of it is new.

I will also check my weights and cap for issues and see where I get. Thanks for the input!

 

[FJcovet]

After several hours of swapping parts around, I finally got it running nicely. I think most of the problem was my idle mixture screw was four turns out.