TBI trouble

Maverick

Maverick

old-school
Location
Anywhere, thanks to my geeky droid
1990 Blazer won't start (turns over just fine) no gas spraying from the nozzles in the throttle body. No gas coming out of the back of the throttle body housing when I disconnect the fuel hose from the back.

I'm guessing the next thing to do is see if power is getting to the fuel pump. If not, figure out why. If so, cry, since it means dropping the tank and replacing the fuel pump.

There's enough fuel in that tank to send a Samurai to Moab and back 3 times. Hmm, that's actually fairly accurate.
 
Have you checked for spark? Modules sometimes go bad on these. If the module goes put it will not have fuel,delivery. I carry a spare module in my Blazer. If you do need a pump, you could cut a hole in the floor like I did. I had an extra piece of the floor cut from another blazer a little larger that the hole, and used some self tapping screws to fasten it down. If I ever need to do a trail repair on the pump, it will be less painful.
 
yes the distributor module is a huuuuuge failure point, and was going to suggest that until i saw that he had no fuel in the fuel lines.

the tbi system uses a module in the distributor that reads the sine wave put out by the pickup coil in the distributor, and converts it into a square-wave signal that is then sent to the ecm. the ecm then counts the square wave pulses and every other pulse, it fires 1 of the 2 injectors in an alternating fashion. that way allows each injector to fire once per revolution of the engine. these modules fail all the time

so no-spark = no injector pulse. but it would still have fuel at the throttle body. check the green wire with a white stripe going out of the ecm and into the fuel line relay it should energize for a few seconds when the key is on, and again once it is running. also check the "crank" signal wire (purple/white i think) it gets power from the "start" position of the key switch and tells the ecm to energize the fuel pump circuit while it is cranking, after it fires and runs the ecm takes over and keeps the pump going

here is a pic i found (i think it is for a 2.8lv6 but it is very similar)
249564_Graphic_37.jpg
 
I have an inline fuel pump with my TBI. It primes for about 4 seconds and then shuts off. Supposedly it is suppose to start pumping again once the ECM sense rpm. I am going to test the fuel pressure today, but I think my pump is not working after the engine starts. My question is can I go to napa and buy a different pump that will just continuously pump when the key is turned on?
 
Jeremed said:
I have an inline fuel pump with my TBI. It primes for about 4 seconds and then shuts off. Supposedly it is suppose to start pumping again once the ECM sense rpm. I am going to test the fuel pressure today, but I think my pump is not working after the engine starts. My question is can I go to napa and buy a different pump that will just continuously pump when the key is turned on?
Click to expand...

The pump will run when there is power applied to it. The ECM controls the fuel pump relay, telling it to turn on and "prime" the system, then when it senses RPM it turns it on again. If you want the pump on all the time, just wire the relay to a switched "on-with-ignition" power source.
 
Jeremed said:
I have an inline fuel pump with my TBI. It primes for about 4 seconds and then shuts off. Supposedly it is suppose to start pumping again once the ECM sense rpm. I am going to test the fuel pressure today, but I think my pump is not working after the engine starts. My question is can I go to napa and buy a different pump that will just continuously pump when the key is turned on?
Click to expand...

it is all in the ecm, it sends a signal to the fuel pump relay to turn it on. once to to prime it for a few seconds, then again when you are cranking the starter (the ecm has a wire that goes to the "crank"position of the key switch so it knows when you are cranking), and a 3rd time when the engine is running at or above idle speeds. it sounds like you aren't getting a "crank" signal so it won't pump when you are cranking, so it won't start and get spinning fast enough for the ecm to take over.

i run a 3 position switch (off/ input #1/ input #2) on my fuel pump relay, input #1 is the ecm signal so that in position 1 it will run as usual, position 2 i have just switched positive so i can turn the pump on at will. and the "off" position will turn the pump off entirely. since it is all separate there is no way for power to back-feed into the ecm and cause damage. i had an ecm that the fuel pump driver went out on and wouldn't send a signal to turn the relay on. so i replaced the ecm and put this switch for if it happens again i'm not stranded

cjncustoms said:
Yeah that's just called simple and easily serviceable. I wouldn't have mine any other way;) and Stratton you run tennis balls as bumps tops:D lol I kid I kid strat!
Click to expand...

i have an inline pump as well. i even carry a spare pump for just in case. i don't think it will fail but its so easy why not carry one?
 
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