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Username Post: Tbi problem        (Topic#364024)
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-18-21 12:11 PM - Post#2812338    

I have a 88 350 tbi that the injectors spray with the key in the run position. The don't do the 2 seconds and cycle off the just continue to spray. Any help would be greatly appreciated.



 
CowboyTrukr 
"10th Year" Silver Supporting Member
Posts: 4568
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
01-18-21 02:19 PM - Post#2812346    
    In response to windwalker

Howdy and welcome.

That would be indicative of stuck injectors. Some people claim that you can actually clean the injector port, but I’m not so sure that’s entirely true. Is this truck your daily driver?

Greg

‘01 Silverado 2500HD 8.1/Allison 1000 Xcab/LB
'00 Explorer XLT 4.0 SOHC V6 Auto
'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500 SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
rockfangd 
"8th Year" Gold Supporting Member
Posts: 3092
rockfangd
Age: 34
Loc: Utica ny
Reg: 04-13-10
01-18-21 05:14 PM - Post#2812363    
    In response to CowboyTrukr

Definitely sounds like stuck or worn injectors.
Not holding pressure.
Probably not getting very good fuel economy either.
I suggest start the engine, then shut it off and watch them when someone shuts the engine off.
See if the fuel pressure leaks down at the injectors. I am assuming it will.


Old School GM fan FOREVER


Edited by rockfangd on 01-18-21 07:39 PM. Reason for edit: No reason given.

 
stumppuller 
"10th Year" Gold Supporting Member
Posts: 931
stumppuller
Loc: Canada
Reg: 11-01-04
01-18-21 06:22 PM - Post#2812369    
    In response to windwalker

Just to clarify, are you saying the injectors are spraying continuously with the key in "Run" and the engine OFF?

-91 Sierra C2500, now K2500
-81 Chev K20


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-19-21 01:19 PM - Post#2812407    
    In response to CowboyTrukr

Yes it is my daily driver. Drove it to work and it ran fine. Came out to go home and would not start.



 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-19-21 01:23 PM - Post#2812408    
    In response to stumppuller

Yes that is correct. Spray is really not the correct word. It is huge amount fuel coming out. The drivers side injector is dumping more than the passenger side.



 
CowboyTrukr 
"10th Year" Silver Supporting Member
Posts: 4568
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
01-19-21 01:52 PM - Post#2812415    
    In response to windwalker

Probably 2 issues going on. Dirty injectors and low pressure. You can check pressure using a TBI test kit. I’d start there first.

Greg

‘01 Silverado 2500HD 8.1/Allison 1000 Xcab/LB
'00 Explorer XLT 4.0 SOHC V6 Auto
'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500 SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3922
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-19-21 02:50 PM - Post#2812424    
    In response to windwalker

Unplug the injector wires and see if the fuel stops flowing. If so look at the wires right by the Top of the TBI unit and the spacer under the air cleaner, to make sure the wires are not pinched or have the insulation rubbed through.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
stumppuller 
"10th Year" Gold Supporting Member
Posts: 931
stumppuller
Loc: Canada
Reg: 11-01-04
01-19-21 03:46 PM - Post#2812428    
    In response to Chevytech

Just an additional note, with the amount of fuel being sprayed into the intake, don't crank the engine anymore. The fuel will all end up in the pan and mix with the oil, and is not good for the bearings.

When you are done troubleshooting and want to begin trying to start her up, do an oil change first.

-91 Sierra C2500, now K2500
-81 Chev K20


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-19-21 05:52 PM - Post#2812431    
    In response to stumppuller

The injectors do stop when unplugged and the wires looked good not pinched or frayed. Should the fuel pump shut of after the two seconds when the key is turned on or keep running. I noticed tonight that it runs as long as the key is on.



 
CowboyTrukr 
"10th Year" Silver Supporting Member
Posts: 4568
CowboyTrukr
Loc: Salt Lake City
Reg: 06-20-09
01-19-21 05:57 PM - Post#2812432    
    In response to windwalker

With the engine off, key on, it should only run about 2 to 3 seconds.

Greg

‘01 Silverado 2500HD 8.1/Allison 1000 Xcab/LB
'00 Explorer XLT 4.0 SOHC V6 Auto
'95 K1500 Z71 EC Short Step 5.7L+0.040/NV3500 SOLD

"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3922
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-19-21 07:55 PM - Post#2812436    
    In response to windwalker

With the injector wires plugged back on the injectors, unplug the distributor 4 wire connector and then turn the key on and see if it sprays fuel.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-19-21 08:42 PM - Post#2812440    
    In response to Chevytech

With the 4 pin connector disconnected the injectors do not spray.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3922
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-20-21 07:03 AM - Post#2812463    
    In response to windwalker

First thing I want to say is do not crank the engine anytime soon after the injectors have sprayed fuel in it because I am concerned the engine could liquid lock and bend a connecting rod. As stated by another member, you will need to change the oil. Take a look and see how far the oil is over filled now and let us know.

Welcome to the board!

It looks like the fuel pump keeps running and the injectors are triggered because the ECM thinks the engine is running.

Is there something under the hood plugged into a wall outlet (120 AC) like a battery charger or heater?
Where is the truck parked?

The electric field oscillating from alternating current can induce enough voltage in the pick-up coil in the distributor to trigger the module causing the ECM to think the engine is running. For all the people that have a TBI vehicle that don't believe this, go out to to your vehicle, take the air cleaner off, turn the key on, and pull the trigger on a plugged in soldering gun with it held under the hood near the distributor. The injectors will spray fuel. Now see how far back you can move the soldering gun and still get the injector to spray. Don't get carried away and floor your engine.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-20-21 02:09 PM - Post#2812492    
    In response to Chevytech

no there is nothing plugged up. The truck is parked in my driveway. You think it might be the ecm?



 
rockfangd 
"8th Year" Gold Supporting Member
Posts: 3092
rockfangd
Age: 34
Loc: Utica ny
Reg: 04-13-10
01-20-21 04:31 PM - Post#2812499    
    In response to windwalker

You are surely on the right track.
Fuel pump should only run for 2 seconds.
Has anything happened recently that could have caused a Ecm issue?
So the injectors and fuel pump relay are getting triggered with ground.


Old School GM fan FOREVER


 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3922
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-20-21 05:44 PM - Post#2812505    
    In response to windwalker

I have never found an ECM causing this problem.

I have never found a distributor module causing this problem.

I have watched distributor modules getting triggered from outside magnetic fields with the key on and engine off.

If the truck is in the driveway and not setting right next to a power company transformer, then I would have the distributor module tested, because they are a very high failure part, and the ECM on these trucks rarely ever fail. I would also try rolling the truck forward or backward a few feet if power lines are buried where you live.

If the distributor module tests good then I would try another distributor module before trying another ECM.

Many auto parts stores will test the distributor module for free if you bring it in.

Make sure when you install or reinstall the distributor module that you use heat sink compound under it. The compound helps dissipate heat from the module. Without it, the module will fail.

I would change the oil after the problem was fixed but before I cranked the engine.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-20-21 06:50 PM - Post#2812508    
    In response to rockfangd

No nothing happened, drove to work in the morning and in the afternoon it would not start and had it towed home.



 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-20-21 06:56 PM - Post#2812510    
    In response to Chevytech

I will try the icm tomorrow if the rain is done and will definitely change the oil before starting if all goes well. I really appreciate all the help.



 
rockfangd 
"8th Year" Gold Supporting Member
Posts: 3092
rockfangd
Age: 34
Loc: Utica ny
Reg: 04-13-10
01-21-21 03:26 PM - Post#2812564    
    In response to windwalker

I agree on the ECM.
Never had to change one for a failure.
I lean toward ICM as well

Old School GM fan FOREVER


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-24-21 03:53 PM - Post#2812840    
    In response to Chevytech

I finally got a chance to replace the icm and the pump and injectors don't run all the time but now i have no fuel spray at all when truck is cranked. Not sure about spark was so mad i came in and mixed me a drink. Will check spark tomorrow lol.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3922
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-24-21 05:17 PM - Post#2812845    
    In response to windwalker

Check to make sure all the wires are plugged onto the ICM well including the pick-up coil wires inside the distributor.

Check to see if it has spark.

If there is no spark, then you should test the resistance of the pick-up coil in the distributor. It should be 500 to 1500 ohms between terminals, with it unplugged.

If it has spark look at the ICM 4 wire connector. A signal needs to make it through it to the ECM to trigger the injectors.


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
rockfangd 
"8th Year" Gold Supporting Member
Posts: 3092
rockfangd
Age: 34
Loc: Utica ny
Reg: 04-13-10
01-24-21 05:28 PM - Post#2812848    
    In response to Chevytech

Inspect the plug at the ICM for the pickup.
Does fuel pump cycle for 2 seconds when the key is cycled on?

Old School GM fan FOREVER


 
scrambldcj8 
"2nd Year" Silver Supporting Member
Posts: 2622
scrambldcj8
Loc: Belchertown, MA
Reg: 04-06-03
01-25-21 04:05 AM - Post#2812867    
    In response to windwalker

  • windwalker Said:
was so mad i came in and mixed me a drink....



No help to offer right now....but this, Love it!! LOL



 
rockfangd 
"8th Year" Gold Supporting Member
Posts: 3092
rockfangd
Age: 34
Loc: Utica ny
Reg: 04-13-10
01-25-21 04:16 PM - Post#2812915    
    In response to scrambldcj8

When you get it running take it out drive it like you stole it.
I always do.


Old School GM fan FOREVER


 
Bill K.b 
Senior Member
Posts: 4498

Loc: upstate NY
Reg: 10-24-05
01-25-21 06:33 PM - Post#2812934    
    In response to rockfangd

I find cussing it out properly seems to help too. Then go have a drink.

Those who can, do. Those who can't, criticize it on the internet.

Driving 2002 Express 2500
2002 Express 2500 extended
1988 G20 conversion
1993 GMC 3500 dually

Plus cars for swap and sale
& yes, I once tried a frame swap on a 51 Chevy.


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-27-21 02:09 PM - Post#2813092    
    In response to Chevytech

finally got a chance to check it and there is no spark. The pick up reads 912 ohms.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3922
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-27-21 05:16 PM - Post#2813108    
    In response to windwalker

Check to make sure the distributor turns when you crank the engine.

Check to see if there is spark at the top of the coil, but it is just not making it though the distributor cap & rotor and coil wire.

Take a test light and connect the probe to the tachometer lead by the coil (white wire) and test light wire connected to ground. Crank the engine and see if the light flashes or stays on steady. It should flicker / flash.

With some test lights it is hard to see the flashing and the light just looks dimmer when cranking.

If the test light connected to the tach lead stayed on steady when the engine was cranking here is a test you can do to test the wires between the the coil and the distributor.
Unplug the two wire connector (Pink wire & white wire) from the outside of the distributor module, and see if they both wires will light a test light when probed while the key is in the on position.

Let me know what you find and I can give you the appropriate test to do next.

For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
windwalker 
Newbie
Posts: 14

Reg: 08-15-20
01-30-21 09:13 AM - Post#2813261    
    In response to Chevytech

I ran the test. Distributor turns when cranked.No spark from top of coil. Can't tell if test light flashes but it does seem to dim when connected to tack wire.Both wires from coil to icm have power with key on. I really appreciate all the help. The fuel pump comes on for a couple of seconds like it is supposed to.



 
Chevytech 
Subject Matter Expert - Senior Member
Posts: 3922
Chevytech
Loc: Twin Cities, Minnesota, U...
Reg: 04-25-04
01-30-21 04:15 PM - Post#2813283    
    In response to windwalker

This is a test you can do that will trigger the module using a 1.5 volt battery.

Connect a spark tester to the output terminal of the ignition coil with the tester ground connected to a good ground.

Unplug the four wire connector from the outside of the distributor

Unplug the two wire connector for the pickup coil inside the distributor

Connect a digital volt meter to the Tach terminal (white wire) by the coil.

Use a jumper to connect the positive end of a 1.5 volt battery to the “P” terminal of the module for the pickup coil and momentarily touch the negative end of the 1.5 volt battery to ground while the key is on and while watching the voltage on the meter connected to the tach lead. The voltage should drop for a moment when the test is done if the module is firing the coil.

Do this test as fast as you can. Just have the 1.5 volt battery connected for a split second.

The coil should produce a spark when this test is done.


For those of you that are wondering why you are not getting replies to your thread:

Did you give the model, year, engine, fuel system type, and transmission information?

If your vehicle has been altered from stock, let us know about that too.


 
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