87 tbi problems

[jgroover]

Ok so heres the story. I bought an 87 state park truck. The guy I bought it from bought it from an auction and said it drove great but he ran it out of gas. After that it would start but not stay running. He put a new fuel filter on it and still the same thing.

I got it to my shop removed fuel filter it was clogged and the fuel tank had a hole in it. Put in new tank, pump, and sending unit. Still the same thing. Removed injectors tonight and no trash in the filter. If I keep revving it up at idle it is fine. If I keep foot off the gas at idle it will die after a few seconds. If I put it in gear and push the gas it bogs down and wants to die. Any help would be greatly appreciated. I work at a dealership but all the guys there havent worked on these things in forever.

[frog210]

fuel pump
collapsed line
another fuel filter hidden?

[79 silverado]

Most likely it sounds like some debris/rest/junk got into the fuel line and is impeding flow of fuel to the injector, esp based on the condition of what was replaced. Running to the bottom of the tank would suck up all the garbage in there.

Can you test the fuel pressure at the line where it goes to the tbi unit to see what you're getting?

Also possible, but slightly less likely, since you work somewhere with repair equipment, do you have anything there to clean and flow test the injector to test the spray pattern, see if it gunked up or partially clogged?

[jgroover]

I don't know if we have any equipment for that, I will find out tomorrow. I couldn't move the line far enough away from the throttle body to test fuel pressure up there. I do have 3 extra throttle bodies at home I could probably swap out. One of the older guys was telling me to just let it run for a long time to see if it would clear up.

[79 silverado]

I doubt the "run it and see if it clears" trick would work here, perhaps had it been a carb truck. If there is a fuel line blockage I suppose eventually the clog could break up and work its way forward towards the TBI, but, I wouldn't be one to wait to try and make that happen myself...

If you're contemplating pulling off the TBI to swap it for another one, then why not just remove the existing TBI and test the fuel line pressure at the TBI connection at that time? It'd give the clearance you need and are lacking currently. It is always possible that the new fuel pump isn't up to snuff and you have low fp, or that there is a line blockage and you aren't getting full pressure. I once had a new out of the box bosch fuel pump for my 88 fiero, which might I add is the biggest fuel pump headache I ever had. Got it back together and it turned out the new pump wasn't putting out the pressure it should've been, had to drop everything again and redo it... Odds are your pump is fine, but, if fuel pressure at the TBI is low, then you know to test pressure at the beginning of the fuel line and see if the pump is good, and if so, then figure out the fuel line clog in between

Basically if you start at the rearmost source and work your way forward you can have confidence in each piece that is behind you. If you work form the end, then from the beginning, there is a whole bunch of stuff that could be contributing or having issues of its own in the middle that was skipped, thats my thought on it...

[crossy]

. I work at a dealership but all the guys there havent worked on these things in forever.[/QUOTE]

LMAO- my local guy cut his teeth on TBI's and he's the man, but that doesn't do you any good. It sounds to me like you have a massive vacuum leak. Pull the air cleaner off and get help to keep it running. then completely choke off the air through the top of the TBI with a rag and see it stays running(idle) or at least if you can hear it sucking through somewhere else. The early TBI's were known for some intake issues. There was also an issue with the base plate gasket getting so hard it would break and pieces just disappear(down the intake) . i don't remember any issue that the gasket caused getting sucked in, but it cause a major vacuum issue. It's cheap, replace it. while it's off make sure there are no ports plugged with carbon as a state park truck it may have just idled a lot.
also with the air cleaner off you can actually see the fuel coming out of the injectors on these set ups. it should be an upside down cone of fuel coming out of both when it's revved a bit. Crossy

[rfmaster]

@jgrover

You can check fuel pressure right at fuel filter by inserting a T at the filter. It should be 9 to 13 PSI for a stock FPR spring. You can check it by applying +12 volts to FP relay pig tail connector - engine does not need to run.. A dead head test can be performed by gently pinching return fuel line (rubber section) - fuel pressure should increase well past 20 PSI.

Make sure that both injectors are spraying fuel. TBI injectors are hardy and rarely fail, but it does happen. However, if injector is not firing just swap injector harness connectors - this way you can verify if ECM injector driver circuit is shoot (also very rare) or not.

Vacuum leaks are known, well documented problem and were discussed previously.

Double check base timing. With EST connector closed it should be bouncing between 16 to 20 deg at idle (600 RPM) and with EST open set to 0 deg by adjusting dizzy (idle around 550 RPM - stock engine). Do not forget to clear SES code afterwards - normal part of procedure.

Reset IAC - search for this procedure on this board if yo do not know.

//RF

[jgroover]

Ok guys so far I have a little above 10psi fuel pressure at the throttle body. Swapped injectors with another set I had from salvage yard runs. It now starts and idles just fine on its own. If I give it throttle while in gear it bogs down and wants to die. One of my coworkers is the thinking the timing might be off, so I will check that and I will post what I find. Thanks so far for all of the information that I have been getting. You guys know your stuff.

[jgroover]

OK timing was way off. Couldn't get a timing light on it so I just adjusted it and now I can step on the gas and it goes. Still need new plugs and wires and stuff.

[crossy]

Hey! you didn't tell us you do JY runs- that changes everything, If you find a nice pair of ----------- ahhh never mind.
look down in the TB with the blades open and make sure that base gasket i mentioned isn't hanging out> good luck with it. crossy

[jgroover]

I replaced that gasket this morning. I tried two of the spare throttle bodys. Gonna put plugs, wires, cap and rotor and hopefully take it for a drive this week. I would really like to pull the motor and replace all gaskets and seals so I don't have to worry about leaks. Motor sounds good. It supposedly only has 71k on the truck but probably did a lot of idling.

[Mr. 250r]

At least you found the majority of the problem i don't know how many people on craigslist decide to swap on carbs because they can't figure out tbi problems

[story]

Hell I'm one of those guys... lol If I didn't have to swap the pump and stuff I prob would have a edelbrock one there...

Hey so do you mind if I ask how you adjusted the timing... A friend told me it wouldn't matter if you moved the distibutor like a carbed engines. Is there a way to do this? If I remember correctly he said it was computer controled?

[jgroover]

Drove it for the first time on the road today. It did good but would die randomly coming to a stop. May need to adjust timing some more and still need plug wires. Going in the right direction though. Steering is extremely loose. Not near as nice driving as my 85 but I did a lot of work on it.

[Zane M]

Originally Posted by story

Hell I'm one of those guys... lol If I didn't have to swap the pump and stuff I prob would have a edelbrock one there...

Hey so do you mind if I ask how you adjusted the timing... A friend told me it wouldn't matter if you moved the distibutor like a carbed engines. Is there a way to do this? If I remember correctly he said it was computer controled?

To set the base timing, you unplug the brown/tan wire to set it to the factory "mechanical" spec.