Carb swap issues please help!

[The dons]

Ok so I have a 86 gmc sierra 2wd short bed 350 I bought a while ago and the previous owner swapped from efi or tbi or what ever stock fuel system it had to a carb setup and said all it needed was a fuel regulator so after buying new fuel regulator new distributor new fuel tank,carb and new electronic fuel pump its still bogging and backfiring and will not stay running....it will start up fine for about 2 mins then starts to act up doing research I found this truck had the esc box under dash and someone already chopped the wires coming from esc bypassing it. So I hooked up a timing light to it and starting it cold (so it would run decent to time it) and the timing light was flashing like it should and I adjusted the time and it was running smooth then it started acting up again and I noticed the timing light wasn't flashing constantly....so my ? Is is there somthing that would stop sending spark after a short while? Please help

 

[AKguy]

Is the new distributor an HEI unit? Did you replace the plug wires?

 

[Knight84]

Make sure the fuel pump isn't too high pressure. Pretty sure carbed systems only need like 5-7 psi. Could be flooding the carb

 

[The dons]

I did install a mr gasket fuel reg knob but I'm going to buy one with a gauge. If that doesn't fix my issue what would be my next step and every thing that has to do with air fuel and spark had been replaced more then once and yes new hei

 

[SirRobyn0]

Yes a carbed fuel system depending on the carb, 5 - 7 is good, if it's an edelbrock even lower. Remember that carbed systems don't need good pressure they need good volume, I'm running 3.5 PSI on my edelbrock. If you have a injection pump in the tank it is possible that it will make so much pressure that it will over come a regulator especially a cheapie like the MR Gasket, so yea it would be good to have a gauge on it, but it sounds like you have an ignition issue. If you have converted to a standard HEI distributor as in non-ESC, if you have full voltage to the distributor you are either looking at a bad coil, pick up or module. Coils and modules are both know to heat up and cause problems.

Another thing to look for would be if it's getting to lean. When it starts to run bad try to keep the choke shut a bit and see if that helps keep it running. Look for vacuum leaks, when the choke is on that can sometimes over come vacuum leaks to some degree, and as the engine warms and the choke opens it starts to run bad.

 

[The dons]

Thank you I'll check everything and I will keep in touch

 

[potent rodent]

are u sure its an 86 i may be wrong but throttle body on a gmc didnt come out till 87 i had a short bed 87 that had throttle body , now the 86 had the sort of computer carb on it . what carb do u have on it ?

 

[The dons]

I have a edelbrock I installed a better fuel reg an gage made a world of difference she still pops but I have more poking around to do but I'm pretty sure I'm getting close

 

[Bextreme04]

I have a edelbrock I installed a better fuel reg an gage made a world of difference she still pops but I have more poking around to do but I'm pretty sure I'm getting close

Run a compression test. Then if you have a low cylinder, back both rockers off, hook up air to that cylinder, and see where you are loosing compression. You can also pull the cap off the distributor and while rotating the crank back and forth about a 1/4 turn and see how far you can rotate the crank before the distributor starts turning. That will tell you if you have a mechanical issue. Generally backfiring or popping will be a mechanical timing issue. You should also hook up a vacuum gauge and see how much vacuum the engine is pulling. You should see somewhere are 20 inhg

 

[The dons]

Okay didnt think of that. I have noticed a big change just with the regulator it used to snap crackel an pop then fall on its face but now it's backfiring less and staying running....and my wife said why can't you just buy a normal car like everyone else.....i did i bought her a new 2017 fusion so leave me an my truck alone lol but yea I will keep everyone updated and thank you for your input an concern ive read so many forums but no one ever says how they fixed it

 

[82sbshortbed]

You'll find the members here are very knowledgeable and very helpful.

Welcome from Texas

 

[SirRobyn0]

Run a compression test. Then if you have a low cylinder, back both rockers off, hook up air to that cylinder, and see where you are loosing compression. You can also pull the cap off the distributor and while rotating the crank back and forth about a 1/4 turn and see how far you can rotate the crank before the distributor starts turning. That will tell you if you have a mechanical issue. Generally backfiring or popping will be a mechanical timing issue. You should also hook up a vacuum gauge and see how much vacuum the engine is pulling. You should see somewhere are 20 inhg

After I did my post I thought about doing another one to mention compression. OP, Bextreme, is right you should do a compression test first, backfiring can definitely be caused by valve issues. You do the compression test and you'll either find the problem, or at least know the engine is good and that the problem is something external.

 

[The dons]

Ok so I was doing some digging around on the web, does anyone think my issues could be caused by vapor lock my fuel reg has no return hooked up?

 

[Bextreme04]

I doubt it... backfiring is not from vapor lock. Vapor lock will cause the motor to not get enough gas and fall on its face once it gets hot. Backfiring says mechanical issue to me.