Robert Kenney
Super Moderator
With the msd the battery powers the box directly so if it is hooked up per the instructions, he's there already.
Weak spark issues
- Thread starter Tonka Toy
- Start date
Robert Kenney
Super Moderator
Tt, can you capture the running issue on a video with good audio? It'll be easier for us to id the problem.
Tonka Toy
Member
I will get that on video asap. It's been sitting out in the driveway during this cold snap, and I decided to bring it into the garage this morning when I got home. Since this was a one man deal, I rigged up my "push pad" (my son's body bag), and was getting ready to move it when I realized steering was gonna be tough. (my garage door is 8x8 and it has to go in at a slight angle at the moment) so I decided to try to start it, so at least the power steering worked. Started right up, and after about 15 seconds, cleared out and ran fine.
aaaaarrrrrrrggghh!!!!
I didn't run it long or take it out on the road, but even sitting on the choke it seemed to have crisp throttle response. The tiniest flick of the linkage made the engine respond right away. Last night at work I was thinking that there could be a fuel supply issue still. Maybe the sock in the tank is plugged or plugging, or there's still a fuel line issue? I did bypass the three way valve for the spare tank since it's not there anymore, back when it was acting up last time, just in case it was plugged, but that didn't seem to help.
aaaaarrrrrrrggghh!!!!
I didn't run it long or take it out on the road, but even sitting on the choke it seemed to have crisp throttle response. The tiniest flick of the linkage made the engine respond right away. Last night at work I was thinking that there could be a fuel supply issue still. Maybe the sock in the tank is plugged or plugging, or there's still a fuel line issue? I did bypass the three way valve for the spare tank since it's not there anymore, back when it was acting up last time, just in case it was plugged, but that didn't seem to help.
Robert Kenney
Super Moderator
Tt, I also suggest installing a fuel pressure gauge to verify proper fuel supply.
Tonka Toy
Member
I've tried for the last three days to upload a video I made showing how it runs, with no luck. I tried uploading it to my photobucket account so I could link to it, nope. I even tried downloading their stupid little app, it doesn't work either.
The problem seems intermittent though. One time I'll start it and it runs fine, except it seems to have a big dead spot between light throttle and heavy throttle. The next time it starts right up but idles like it's lacking spark or fuel. Of course, this is as it sits in the driveway, I'm not into getting a tow bill. Anyway, that's about how I can describe it. I'm not sure what else to say about it.
The problem seems intermittent though. One time I'll start it and it runs fine, except it seems to have a big dead spot between light throttle and heavy throttle. The next time it starts right up but idles like it's lacking spark or fuel. Of course, this is as it sits in the driveway, I'm not into getting a tow bill. Anyway, that's about how I can describe it. I'm not sure what else to say about it.
Robert Kenney
Super Moderator
Youtube is easy as pie. Upload from a smart phone or computer.
Put a fuel pressure gauge on it. Get some real data to go on at the moment we are all guessing.
Put a fuel pressure gauge on it. Get some real data to go on at the moment we are all guessing.
Tonka Toy
Member
Sorry for the delay in response. I've tried about every avenue I know to upload a video, or even a link, and it's proving to be a bigger pain than fixing this truck. I have a youtube account, but I rarely use it, because I'm just not into knowingly giving google any more information about me. And every time I log into any google based account I have, my computer does crap I don't like for days afterwards. And somehow even my photobucket links won't work. I'm guessing it's something to do with security issues on this site. And I'm totally ok with that. So I don't know if there will be a video here.
Recently I haven't a lot of time to mess with it, but here's what I did do. I verified that the fuel tank was clean inside and that the sock on the end of the pickup wasn't plugged. Since there was no sock,… so then I rigged up a gas can with a line straight to the carb. No fuel lines from the truck to worry about. No real change. Then I ran a jumper wire from the battery and essentially hot wired it, so there was nothing coming to the coil through the ignition switch or the truck wiring. No change.
it will start right up, but sometimes it runs like it's slightly flooded until it runs for about 30 seconds. Then it runs well. But if I drive it, or just power brake it, after about 10-15 seconds with a load it just starts dying out. I can then return to an idle, and it runs fine. And it will do that as many times as you want to sit there and try it. So since it comes and goes suddenly, I'm leaning towards an ignition problem.
About the only thing left that I can't verify is the ignition pickup in the distributor. And since there doesn't seem to be any shops around anymore that can diagnose vehicles without an obd2 system, god only knows if it's acting up or not. But since I'm looking to go GM TBI, I'm undecided as to what to replace it with. I have two Holley distributors that I could also convert to whatever. I'd like send off one of my holleys to get the GM small cap hei from the TBI setup grafted onto it. But after I get that back, I don't yet know how to wire that up to work with my carb until I get the efi ready to install. Seems that no matter what I do, I'm dropping about $150 on the distributor, so I don't want to do it more than once. Some research is in order.
Recently I haven't a lot of time to mess with it, but here's what I did do. I verified that the fuel tank was clean inside and that the sock on the end of the pickup wasn't plugged. Since there was no sock,… so then I rigged up a gas can with a line straight to the carb. No fuel lines from the truck to worry about. No real change. Then I ran a jumper wire from the battery and essentially hot wired it, so there was nothing coming to the coil through the ignition switch or the truck wiring. No change.
it will start right up, but sometimes it runs like it's slightly flooded until it runs for about 30 seconds. Then it runs well. But if I drive it, or just power brake it, after about 10-15 seconds with a load it just starts dying out. I can then return to an idle, and it runs fine. And it will do that as many times as you want to sit there and try it. So since it comes and goes suddenly, I'm leaning towards an ignition problem.
About the only thing left that I can't verify is the ignition pickup in the distributor. And since there doesn't seem to be any shops around anymore that can diagnose vehicles without an obd2 system, god only knows if it's acting up or not. But since I'm looking to go GM TBI, I'm undecided as to what to replace it with. I have two Holley distributors that I could also convert to whatever. I'd like send off one of my holleys to get the GM small cap hei from the TBI setup grafted onto it. But after I get that back, I don't yet know how to wire that up to work with my carb until I get the efi ready to install. Seems that no matter what I do, I'm dropping about $150 on the distributor, so I don't want to do it more than once. Some research is in order.
Tonka Toy
Member
a little update on this truck. Please note that I did not Say quick. 
after last posting here, it sat for about a month. I went out to move it one afternoon and found that the new fuel pump wasn't pulling any fuel. I think I had two bad pumps in a row. My original and the replacement. So I decided to try an aftermarket electric one, and then it wanted to run just fine. For a few days anyway. But this time when it acted up, it was also having idle issues. Never the same idle speed. On top of running rough and such.
so I got it home and went to work. Timing was all over the place, and when I went to move the distributor, it was too hot to touch with my bare hand. wait,.. What?! It's not cool that it's not cool. Lol! After it cooled off, it seemed to act better. Aha!! I suspected my hot ignition was the culprit, but it hasn't proven to be true yet. Going back to stock hasn't helped it's condition and robbed it of power and milage. There's got to be a internal problem with the prestolyte. So I decided to do the mopar/Holley/GM distributor conversion that bill hamilton talks about in the efi section. Mainly because it's compatible with the efi and will give me the timing control I want, whenever I get around to the efi. Anyway, talk about easy! Now it runs sweet! I'm not currently running the msd box, but I will add that to the system again soon. Only the hot coil remains.
A couple of days later, while going home, I needed to speed up to make a lane change. I was rolling along at about 35 and just punched it. And to my utter amazement, for the first time ever, the seat slapped me in the back! 
so at this point, I'm 99% convinced that it's issues are resolved. But I still wonder if I've only masked the problem. The only way to know for sure is to drive it every day, which I'm glad to do.
after last posting here, it sat for about a month. I went out to move it one afternoon and found that the new fuel pump wasn't pulling any fuel. I think I had two bad pumps in a row. My original and the replacement. So I decided to try an aftermarket electric one, and then it wanted to run just fine. For a few days anyway. But this time when it acted up, it was also having idle issues. Never the same idle speed. On top of running rough and such.
so I got it home and went to work. Timing was all over the place, and when I went to move the distributor, it was too hot to touch with my bare hand. wait,.. What?! It's not cool that it's not cool. Lol! After it cooled off, it seemed to act better. Aha!! I suspected my hot ignition was the culprit, but it hasn't proven to be true yet. Going back to stock hasn't helped it's condition and robbed it of power and milage. There's got to be a internal problem with the prestolyte. So I decided to do the mopar/Holley/GM distributor conversion that bill hamilton talks about in the efi section. Mainly because it's compatible with the efi and will give me the timing control I want, whenever I get around to the efi. Anyway, talk about easy! Now it runs sweet! I'm not currently running the msd box, but I will add that to the system again soon. Only the hot coil remains.
A couple of days later, while going home, I needed to speed up to make a lane change. I was rolling along at about 35 and just punched it. And to my utter amazement, for the first time ever, the seat slapped me in the back!
so at this point, I'm 99% convinced that it's issues are resolved. But I still wonder if I've only masked the problem. The only way to know for sure is to drive it every day, which I'm glad to do.
Scoutboy74
Moderator
Sounds promising. As long as this issue has been vexing you, I hope you finally turned the corner on it.