Question about 1991 Chevrolet C1500

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90 chevy 4/4 pu tbi 350 floods out

I have a 1990 chey 1500 siverado 4/4 pu with TBI 350 engine. I caught wiring harness on fire as it backfired through the carb and caught on fire. I replaced all the wires frome a 1989 chevy same model all wires semed to mach up ok. I was haveing trouble with it starting any way so l took the injectors off and sprayed carb cleaner on them did not pop them out of their schell. I have replaced them with the 89 injectors distibutor with new wires rotor and cap. The above info is probably not revelant as the truck has the same problem as before it does not want to start. It is in time because it will start ok some times but it floods out after you rev it up then it craps out and starts to miss, I know it is getting too much fuel cause it seems to be flooding out. Put your foot in the trottle and crank and it eventually may start. Why is it flooding out and how do i fix it . TBI carbs are hard for me as i can work on a older carborator and fix it . Hope you can help me make this thing run as i really need the truck to run. Please Help Thanks Will Potter Urbana Mo. PS i forgot to tell you i put a new roller timing chain on as i thought the chain had slip[ped but that was not the issue!

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I'm having the same trouble with the flooding after warm start...if it's the temp sensor, would the temp gauge be working? It's in a 1991 Chevy van with an injected 350 carb.

Posted on Jul 25, 2010

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Hi, the engine controller uses the coolant temperature switch to adjust fuel flow rate of the injectors. is it disconnected? or perhaps not making good connection in the harness? the little two wire harness that goes to the switch goes bad all the time. wiggle it, if it seems to start when wiggled, there's your problem. other thing is, when you had a fire, did the TBI get burned? the gaskets inside will leak fuel if cracked/bad. you may need to rebuild the TBI. it's not hard at all, get a rebuild kit from your local parts store and the instructions will tell you how to, but check it by shining a flash light in the bores, when the key is turned to the on position, the injectors will spray four times to give gas to start the vehicle, if you have someone turn key on and you watch the fuel spray at same time, see if there is any leak down other than 4 sprays.

Posted on Jul 08, 2010

Testimonial: "Your help was dead on the coolant temperature switch was bad, replaced it and it starts ok now. Thanks soooo much for your help, it helps keep the peace in the family. Keep up the great help you give us back yard mechanics! I am glad there are folks out there willing to help us out when we need it THANKS AGAIN!"

  • Brian Kinney Oct 17, 2011

    You rule, my 1991 chevy plow truck had the same problem. I changed the temp sensor and now it runs perfect. Thanks. Brian K.

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You never said the mileage but that being said this is a 20 year old vehicle and I suspect your most likely issue to be dripping fuel injectors. If you check a manual you can put an ohmeter across them(does yours have one or two?) and check them electronically. It seems like you already had a hunch in this direction. Seafoam.com is a superb product -- the stoddard solvent is actually used in the airplane industry!

But a pressurized cleaning by a shop might help but they can run $200 and you get no parts for that so I'm with the guy who said rebuild it --on that issue.

I disagree with the coolant temp controller.Your system computer is called OBD I and it was very simple. Usually the fault codes could be brought out by place a paperclip across two terminals under the dash and the codes will blink, like morse code, through the dash check engine light. I've done this many times on many GM products for OBD I. These comps run in a standard SaFETY mode until the engine is warming up 3-5 minutes later.

Another quick check you can do is to watch the TBI injector, even put a piece of white paper in there then have a helper turn the key, leave it 2 secs , turn it off, turn it to ON, not vcrank 2 mor secs.... if the paper is wet then you definitely have a dripping/leaking TBI carb unit. This is more sure than the electrical check. What it does is each 2 second pulse turns on the electric gas pump(I hope yours is elec, some trucks of that era were weird crossbreds... even TBIs could be odd. So it brings the fuel pressure up to FULL without running the engine at all... do this all COLD. If it leaks I'd rebuild or replace the TBI carb module for sure.

I'd price a new TBI carb or a reman. How;s your MPG? Iff it is extra low this is almost assuredly the main issues.

Posted on Jul 14, 2010

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What causes the injectors to spray 4 times. I have a 454 TBI that will not spray for start up but will start and run fine if I poor gas into the throttle body and crank it up. Thanks for any help.

Posted on Jul 13, 2010

  • matthew Dec 02, 2010

    hi, i wanted to set the record straight on the start up spray of the tbi, when cranking, the engine controller fires off the injectors about 4 times before it starts. the 4 times is due to the number of cylinders before ignition occurs at top dead center in most cases when the engine is cranked. Generally, if no spray at first, check for immediate fuel pressure getting to the rails and injectors. the fuel pump has a one way valve that can go bad and allow the fuel in the fuel rails and injectors to relieve the pressure back into the tank and when cranking, the pump has to build the pressure again. The coolant temp sensor if malfunctioning and showing the engine is overhot(over 260 degrees) can tell the computer to lean out the injectors at start up also. the only other thing i could think of is a distributor wiring problem. the distributor send signal through the ignition control module to the ecm to tell the ecm to fire the injector drivers per each cylinder revolution. if the distributor or wiring has bad connection, this might be the case.

  • akridgewayne
    akridgewayne Jan 15, 2013

    could it be a fuel regulator problem letting to much fuel pressure into the injectors

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