1987 Chevy Truck Issues (TBI)

[sg5492]

OK... This is what I have. I see a red wire that's hanging out on the one on the left. So the one on the left is for testing power to the fuel pump, what is the box on the right for? Just curious.

[hatzie]

OK... This is what I have. I see a red wire that's hanging out on the one on the left. So the one on the left is for testing power to the fuel pump, what is the box on the right for? Just curious.

One is the FPR the other is the fuel module for vaporlock that I mentioned in my last post.
If you feed 12v to the red wire the selected fuel pump should run.  This assumes the tank switch on the dash is ok.

My Droid from orbit

[Irish_Alley]

on my 91 v3500 i have the one on the left(with the red wire) and nothing on the right. theres a spot for it just nothing there.

[Captain Swampy]

A noid light plugs in place of a fuel injector. While cranking the engine it needs to flash. If it doesn't come on or stays on continuously there is a problem. No flashie= No workie 

[frotosride]

Well you said you hear the pump in the tank  once the key is on...so it may be something simpler. Like fuel filter, return line clogged or the actual tank selector switch failing.

[AZ87V10]

So how come it appears that not all trucks have that second relay? I have an 87 with factory TBI and fully functioning dual tanks and I only have the one relay on the left? My truck runs fine regardless of which tank is selected, although I tend not to use the driver's side tank since it leaks when it's full.
I've noticed it seems like the early TBI systems were a finicky beast. If they're not tuned just right and in tip top shape, they tend to not run right. My truck seems to run rich and has an intermittent stalling issue when the engine is cold and also backfires through the exhaust when cold for example. I've thrown all kinds of parts at it with little change. It's better than it used to be but not completely right. Tired of throwing parts and money at it.

[hatzie]

So how come it appears that not all trucks have that second relay? I have an 87 with factory TBI and fully functioning dual tanks and I only have the one relay on the left? My truck runs fine regardless of which tank is selected, although I tend not to use the driver's side tank since it leaks when it's full.
I've noticed it seems like the early TBI systems were a finicky beast. If they're not tuned just right and in tip top shape, they tend to not run right. My truck seems to run rich and has an intermittent stalling issue when the engine is cold and also backfires through the exhaust when cold for example. I've thrown all kinds of parts at it with little change. It's better than it used to be but not completely right. Tired of throwing parts and money at it.

The hot fuel handling module is only on certain engine and GVW combinations.
Download the drivability and emissions manual for your rig. 
They aren't that finicky or complex.  They don't respond well to shotgun repairs.  You'll spend a bunch throwing parts at it and probably wont fix it.
Plug in with a cheap $100 laptop and a DIY ALDL cable running free software... TUNERPRO or WINALDL and watch sensor behaviour when she misbehaves.
A Fuel pressure gauge and a decent $50 DMM like the Extech 330 are your friend too.

Don't assume new parts are good or meet spec...  most are made in China now.

Sent from my SM-P605V using Tapatalk

[frotosride]

The hot fuel handling module is only on certain engine and GVW combinations.
Download the drivability and emissions manual for your rig. 
They aren't that finicky or complex.  They don't respond well to shotgun repairs.  You'll spend a bunch throwing parts at it and probably wont fix it.
Plug in with a cheap $100 laptop and a DIY ALDL cable running free software... TUNERPRO or WINALDL and watch sensor behaviour when she misbehaves.
A Fuel pressure gauge and a decent $50 DMM like the Extech 330 are your friend too.

Don't assume new parts are good or meet spec...  most are made in China now.

Sent from my SM-P605V using Tapatalk

I second these motions...espe ially the last one it has bitten me a few times!! Never say ' it's a new part so that can't be it'. That's the first place to look!

[Captain Swampy]

So how come it appears that not all trucks have that second relay? I have an 87 with factory TBI and fully functioning dual tanks and I only have the one relay on the left? My truck runs fine regardless of which tank is selected, although I tend not to use the driver's side tank since it leaks when it's full.
I've noticed it seems like the early TBI systems were a finicky beast. If they're not tuned just right and in tip top shape, they tend to not run right. My truck seems to run rich and has an intermittent stalling issue when the engine is cold and also backfires through the exhaust when cold for example. I've thrown all kinds of parts at it with little change. It's better than it used to be but not completely right. Tired of throwing parts and money at it.

There is a ton of information at tbichips.com. Also check for a vacuum leak at the throttle shaft. Brooke's was worn and it made the truck run like crap.

[AZ87V10]

So how come it appears that not all trucks have that second relay? I have an 87 with factory TBI and fully functioning dual tanks and I only have the one relay on the left? My truck runs fine regardless of which tank is selected, although I tend not to use the driver's side tank since it leaks when it's full.
I've noticed it seems like the early TBI systems were a finicky beast. If they're not tuned just right and in tip top shape, they tend to not run right. My truck seems to run rich and has an intermittent stalling issue when the engine is cold and also backfires through the exhaust when cold for example. I've thrown all kinds of parts at it with little change. It's better than it used to be but not completely right. Tired of throwing parts and money at it.

There is a ton of information at tbichips.com. Also check for a vacuum leak at the throttle shaft. Brooke's was worn and it made the truck run like crap.

Thanks Captain! I know you've mentioned that site before, just haven't checked it out yet. I rebuilt the entire throttle body like a year and a half ago or so and replaced the base gasket. The problems I described were there from day one, but were diminished after that. All other major tune up parts have been replaced new in that time as well. I don't drive the truck much, I've owned it for three years and have only put about 7500 miles on it! Would some of these symptoms be emissions related? I still suspect fuel as well since the truck stumbles on start up once it's started warming up. It cranks and fires just fine with a cold engine. There's also no codes being thrown. The service engine light operates on start up as it should.