I Need /Help Adice, Ideas

[Already Gone]

I was driving home from a friends yesteday doing 65mph on the highway when all of a sudden the the truck lurched, hesitated and started missing. I looked at the gauges and they were all reading normal except the factory tach was flopping all the place going up to 5000rpm and then bouncing back to 0 and everywhere in between. I shut off the key pulled over and after I stopped tried to start the truck and it fired right up and ran normal at idle. I got out ,opened the hood and everything seemed normal under there too. When I put the truck in drive it started to buck some more and I feathered it and it got up to 50mph and it wouldn't go anymore. For the rest of the 5 mile drive home from there it bucked and hesitated and stalled about 10 or 15 times. Does anyone know what what might be wrong. I bought the truck in 2001 the way it is and I think it has the HEI ignition on it. This truck has ran perfect and I've never done anything to it in the 10,000 miles I've put on it since I bought it. In my limited knowledge I'm thinking a distributor/electrical problem. Anyone got any ideas on this? The pics were taken this morning.

[68gmsee]

The way you're describing it could be any of a lot problems.
How does it run idling in neutral? It could be fuel related like clogged filters, dirt in the carb bowl, fuel pump, etc. or it could be mechanical like jumped timing or maybe electrical as a ground, battery or alternator.

You will probably have to isolate it to either electrical, mechanical or fuel.

I had one that had a bad alternator and it woud run okay on battery power and as the batter would get run down start missing and couldn't get any speed out of it. When I stop for a while, the battery charged up a bit and it would run for a few minutes again. Never saw the problem in the guages.

[68gmsee]

Just reread your post and I saw where you mentioned it ran okay idling but missed out when you put it in drive... Does this happen everytime the same way?

[Professor]

Check your ignition coil (mounted on the top of your electronic ignition cap). When the insulating material between the primary and the secondary windings of the coil begins to break down, it can act the way you describe. Often, when it is acting that way, if you let it cool down (the coil) it will run fine until it warms up again.

(Legal disclaimer: any information provided by me is purely speculative, but based on too many years of practical experience -- and my regular teaching of some university courses in the mechanical technologies. Use it with your own good judgment.)

[Already Gone]

Originally Posted by 68gmsee

Just reread your post and I saw where you mentioned it ran okay idling but missed out when you put it in drive... Does this happen everytime the same way?

Yes as soon as it goes into drive it starts missing and hesitating. I bought a new fuel filter last week I guess I'll start with that. If I had fuel pump poblem would that show up when its idling ?

[Shyguy]

I had a similar problem with my '71 C-10 a few months after I bought it. It has the same Hei distributor that you have.

I tried the fuel filter and replaced some near collapsed rubber fuel lines, but the problem did not go away.

I removed the distributor cap and saw that the rotor and cap were in sad shape, in fact the worse I have ever seen and still run. I decided since I was going to replace the cap and rotor I might as well replace the coil also. It has ran fine ever since.

Danny - Southeat Missouri

[Already Gone]

Originally Posted by Shyguy

I had a similar problem with my '71 C-10 a few months after I bought it. It has the same Hei distributor that you have.

I tried the fuel filter and replaced some near collapsed rubber fuel lines, but the problem did not go away.

I removed the distributor cap and saw that the rotor and cap were in sad shape, in fact the worse I have ever seen and still run. I decided since I was going to replace the cap and rotor I might as well replace the coil also. It has ran fine ever since.

Danny - Southeat Missouri

Thanks Danny, I've never had one of these apart but I'll do that right away. I think its more electrical than fuel.

[cameeks]

Originally Posted by Already Gone

I bought the truck in 2001 the way it is and I think it has the HEI ignition on it. This truck has ran perfect and I've never done anything to it in the 10,000 miles I've put on it since I bought it.

Man that is some old oil then

One problem is is that you dont know how long it has been since the PO changed anything. The PO could have done a tune up a month befor you got it or 5 years befor you got it.

[hvychve]

Alot of good tips and ideas, I once hit the road in my truck years back and it idled fine, when driving it would start burpiing and freaking out, I had a pickup wire ( from the pickup coil -inside the dist. to module) starting to break and when I started to drive vacuum would pull on my vacuum advance and move and advance my timing , this would cause the breaker plate to move and flex the pickup wires causing similiar issues, it does sound like you have an ignition issue of some sort with the rpms shifting the way they are, it is sorta hard to describe how to test each one without proper equipment, I use and oscilliscope to check coil output (around 35,000 volts) the pickup coil can be checked with a frequency tester or scope, hand held or whatever, hook up to both leads of pickup coil and have someone crank it, should see about 1 and a half volts high and low , also try wiggling the wires while cranking to see if any glitches show up on scope, and as far as the module, well, a scope is best to test that , but, you could take a stabe and buy a rebuilt dist. not too costly, it should come with pickup and module, you might want to stab a new coil / cap / rotor while your at it , one note, dont forget the ground strap just under the coil, I have also noticed that some cheaper caps will tend to ground out on the coil mounting screws, you can see this by looking at the bottom of cap to see if any unusual burn marks next to wire terminals in cap. good luck.

[blue 71]

with your tach doing what you said, i would check to see that
your tach wire isn't shorting against your coil wire. had this happen
to me. the two terminals are very close. good luck

[Already Gone]

Thanks for all the help and advice. I managed to get the cap off and here is the pic of what was underneath. Now I do know that this engine came from the factory with the old breaker point distributor (its a 1967 396) so that means this HEI distributor was added after. How new or old it is I have no idea so again I'm asking for help on how it looks inside. I can get a new coil, pickup, cap and rotor or just put in a barnd new ( for not a lot more than the sum of the parts ) MSD Street Fire HEI Ignition Part # 8362. has anyone installed one of these ignitions on their truck?

[byrd]

I put a 65k volt billet style HEI in my truck from Skip White off ebay for about $50-60. Popped it in 2 years ago and problem free ever since The jump from around 40k volts(stock) to 65K is a noticable difference in torque and HP. For the $$ I would just swap the HEI out and throw that one in the recycle bin, as they are not worth anything really. Just my .02....Randy