Engine rough, arching on coil...vacuum leak or...?

[sproggy]

...Morning folks. So the '71 with the F155, Weber , Delco distributer (old Manafre hack) and headers was driving great after I changed some radiator hoses and flushed the engine, put in new fuel pump, battery, and starter. Running better than ever. Pulled out from an intersection and suddenly feels like it is running on 5 cylinders. I limped home as I wasn't far and pulled off the spark plug wires 1 by 1. Was getting spark to all and engine dropped as I pulled them off so that did not seem to be the issue but as I pulled off the one to the right of the coil (which did spark with the spark plug terminal) the center of the coil started arching with the negative terminal on the coil. I don't ever recall seeing that. Might that indicate my problem? I also thought I might have a vacuum leak but I didn't notice any engine change when spraying carb cleaner around the manifold.
I also have had some thoughts in the past that I may have a head gasket leak as I was noticing a lot of white smoke but mostly (though not only) at start up. One thought was that flushing the engine aggravated this condition. My mechanic buddy thought to pull carb and check for cracked manifold, too. But firstly, is this normal behavior of the coil?

On an unrelated issue, truck seemed to run much better with the new fuel pump with no hesitation under load. I was under the impression fuel pumps failed all at once but could one be half working for a long time and supply fuel but not 100%...causing the hesitation under load? I wouldn't think so but....

Thanks all, top of a Landcruiser morning to ya!

Sproggy

 

[Solace in Solitude]

I’ve never noticed the arcing... do, I can’t comment either way. @FJ40Jim told me a coil doesn’t really fail, unless it dumps it’s oil out.

I’d lean more toward suspecting plug wires or fuel delivery.

My thoughts are:

1. Old plug wires, including the coil to dissy wire?

2. Is the coil leaking oil?

3. Is the fuel filter old?

I’d start with the easy stuff... replace old plug wires... replace fuel filter...

If your soft fuel hoses are old, replace them... flush out the hard fuel lines.

Clean the carb inlet fuel screen, if you have one... spray some carb cleaner into the carb, with the engine running.

A mechanical fuel pump can fail a little at a time... an old diaphragm can become brittle and develop a pinhole that slowly (or quickly) becomes a failed diaphragm and dumps fuel in your crankcase... does your dipstick smell like gas?

By “under load”, do you mean uphill, foot buried in the accelerator pedal? If you have any place that air can get into your fuel delivery system, it will present “under load”... cracked soft lines, bad clamps, filter not sealed well, etc.

If you feel you may have a head gasket leak, perform compression tests and see how your readings are... it’s cheap (rent a kit from an auto parts, they refund when you return it). Follow the instructions and be sure you have the engine warmed up, the throttle wide open and no choke.

Good luck!

 

[Jaric00n]

Maybe an airline crack on the coil itself letting it arc to the GND of your coil rather than to the dizzy and plugs?

 

[sproggy]

Thanks guys. I surely confused the issue by addressing more than one thing in my post. I'm pretty sure it's not a fuel issue. Not the coughing engine issue I'm experiencing, at least. That hesitation thing had been a forever problem with the truck and in replacing the fuel pump which had completely failed it seemed to be much improved so I was just wondering.

The main problem I'm dealing with now is the engine choking coughing and sputtering. It is undriveable in this condition. It happened all of a sudden. Drove around for 30 minutes all system go, running great. Pulled away from an intersection and suddenly running crappy but didn't die. Once home, I pulled off the wires one by one and the engine dropped speed each time. This tells me that the cylinders are all firing thus the spark is indeed arriving at the cylinder as is the fuel. Saw a strong spark leaping from the spark plug lead to the spark plug terminal, too. So that seems good. What I did notice was the arching between the center of the coil and the neg. terminal. That seemed odd but I'm kinda dumb. If there was some problem with the spark, despite this arching, I would think I would not have such a strong regular spark to the plugs.

I think I need to do a leak down test and compression test, yeah? Can I pull the hose of the brake booster and plug it...to eliminate that possibility without screwing anything up?

 

[morganism]

Is prob the coil and ignitor ground. This has the ignitor pack and coil mounted to the distributor body ?

Best solution is to remove the mounting bracket for both, and clean the mounting bolts well. Then run a new, seperate wire from the corner of the ignitor pack to a solid ground. You should see a small ground wire in one corner of the ignitor case, so use the other corner for the new ground wire.

Coughing and lagging are usually an EGR problem, Try sucking on the vac hose while truck is running, doing it quickly while tapping on the tophat of the EGR might release the little carbon rocks in there. Do NOT tap on the EGR cooler - ever. It contains lots of gremlins.....

You should also pull the dist cap, and soap and water clean inside. If any wear on parts in distributor, metal filings can line up inside, and cause a magnetic field that can cause magnetite in dirt to line up, and create a trace on the outside of the cap. Do you have the cap vac line attached on that model? If you grab that while it is running, you can get a shock!

I think stock model also has a oil feed on the top of the shaft, give it a soak in 2 stroke (non-detergent) oil.

 

[cruzer971]

I had a Chevy that would do the coughing sputtering thing, but it was intermittent. Turned out to be the plug wires. Check the resistance on each one, or replace them.

 

[sproggy]

Well guys I messed up, I think. I looked at it again with a friend and we determined that two of the cylinders are not firing (the two to the right of the coil). I assume they weren't when I looked earlier, as well, and some how I didn't have my head screwed on correctly. What I find strange is I am pulling the leads off the spark plugs and getting shocked. I have gloves on and using rubber handled pliers. When I pull the wire it starts arching at the coil or somewhere that I can't see (I can hear the clicking of the arc) and I am getting shocked when I lean against the tire! I can't remember this ever occurring. It is a new battery, does this play a part?

This is a 1971 simple set up, apart from having the delco dizzy it is stock. Coil, dizzy, points, condenser. I don't have any emissions stuff on it. I am planning on getting the equipment tomorrow for a compression and leak down test but until then, does this shocking business seem odd?

 

[Solace in Solitude]

No guarantee it's the plug wires... But, as I said before, I would replace them first... Maybe this will help put it into perspective. Why car’s spark-plug wires can zap you

 

[sproggy]

Thanks, it could indeed be the wires. That would certainly beat a blown head gasket. It seems strange to me it would be two of them at once but I'm no expert by any means.Thanks for the link!

 

[Solace in Solitude]

I replaced all plug wires and dissy cap when I bought my truck... Just cheap insurance.

 

[sproggy]

The cap I've replaced plenty of times though it probably never actually needed replacing. But as you said, cheap insurance. Not sure about the wires. NOt recently for sure.