Throttle body issues

[Chrispbrown36]

I recently put new intake gaskets and valve cover gaskets on my 87 V10. After putting it all back together she wouldn't fire up. I noticed that there wasn't any fuel coming out of the injectors, so I poured some down the bore and she fired and died. I suspected the injectors so I tested with a 9V battery and could hear no clicking. But I have never tested injectors before and I wonder if the 9V is enough to get a reaction. I am also wondering about the ignition module, since I have no idea when it was last changed. What do you guys think?

[Oldriginal86]

I think parts don't go bad just by removing then reinstalling. Go back and check every connection. If there's no fuel at the injectors, can you hear the fuel pump prime the system when the key is turned on? I may be getting ahead of myself. Did it run prior to the intake gasket install? Check for pinched wires under the intake. I hate to say it but I hear it from customers often, "I know it couldn't be something I did". I've been turning wrenches professionally for 40 years and still make mistakes. We all do. You'll fix it, go back and check over your work. Good luck and keep us posted.

[D13]

SO, if you prime it and it fires than the spark is there which says the distributor is close and the module is at least functional. So no fuel is either pump failure, relay failure, ECM failure, or wiring. Assuming it ran before, most likely is disconnected wiring harness, check at fuel pump relay first. When you turn the key on without cranking the ECM commands the fuel pump to run for a couple seconds. If it does that then there should be pressure at the fuel rail tap. But my bet is a disconnect between distributor, ECM, fuel pump relay, or injector harness.
You did make sure the ground wires at the back of the engine are hooked up, right? Grounds are critical on injected motors.

[Chrispbrown36]

Yes she ran fine before the gasket change. After I posted last night I got to thinking about it and realized the module was out because it would fire with gas poured down the bores. Yes the fuel pump does prime when the key is turned. And there is fuel present in the bowls where the injectors sit on the meter assembly.....which is what makes me think injectors. It is perfectly possible I missed something when hooking it all back up, but I have gone back over it a few times and still am not seeing anything that isn't connected. Where are the grounds at the back of the engine specifically?

[Chrispbrown36]

Ok, so the truck still will not start. I have tested everything I can think of. Fuel pressure is fine, fuel is making it to the bowls the injectors are sitting in, I am getting voltage from the injector harness, ECM fuses are fine. I tested the injectors for resistance and I get zero ohms on them. I have tested the injectors with a 9v battery and there is no click. I have gone back through the connections and still can not find anything that I might have missed. I keep reading about grounds on the back of the heads and found a ground wire on the rear passenger side that is intact.
At this point I am really leaning toward the injectors being bad, but I haven't ruled out the ignition control module since I have read that if it has gone bad it will not tell the computer to fire the injectors.

[Chevy3+3]

Some may not believe me at all but I had the exact same issue your having.....I think. Here is what happened to me.

I drove my perfectly running '88 V30 454 into my garage to start my transmission swap. While it was down I decided to swap intakes because I thought my original high mileage gaskets were leaking. I pulled the harness out of the way, pulled distributer, removed old intake and then reinstalled everything just as it was taken apart. Next step was to start it up and a NO GO! I checked things over several times and could not figure out anything. My injectors were pulsing fuel when I was cranking but my truck was dead in the water. I triple checked making sure that I didn't stab the distributor back wrong. My truck would not try and start at all. I was pulling my hair out because I drove it into the garage before I tore it apart. Turns out I wasn't getting fire/consistent fire.

I spoke with a good mechanic who I trust and told him my symptoms and he said replace the distributer. I was confused and asked why. He said he has seen in the passed that when a worn distributer is removed that the tolerances change between the pickup coil and magnetic reluctor ring causing it to not start. So I went and looked at my distributor and saw where the little triangular shaped cogs on the reluctor ring were making contact when they shouldn't be. They should be very close to touching but if they touch anywhere then it wont allow the truck to start.

So I ran to the parts store (oreilly's) and bought a cheap complete distributor for around $100. It came with everything including a new cap. I stabbed it in and hit the key and the truck fired up and purred like a kitten. I usually would not think taking something apart could cause a part to go bad but when it happened first hand to me I believe it.

So I say to you to inspect your distributor or try another and see what happens because it sounds very similar to what happened to me. Good Luck

[GM_For_Life]

Originally Posted by D13

SO, if you prime it and it fires than the spark is there which says the distributor is close and the module is at least functional. So no fuel is either pump failure, relay failure, ECM failure, or wiring. Assuming it ran before, most likely is disconnected wiring harness, check at fuel pump relay first. When you turn the key on without cranking the ECM commands the fuel pump to run for a couple seconds. If it does that then there should be pressure at the fuel rail tap. But my bet is a disconnect between distributor, ECM, fuel pump relay, or injector harness.
You did make sure the ground wires at the back of the engine are hooked up, right? Grounds are critical on injected motors.

Had an 88 v10 that did something very similar to OP's problem, replaced the ECM after much heartache and it fired right up. Above are the usual suspects

[Chrispbrown36]

I am at the end of my rope on this. I have done everything but rip the intake and valve covers back off and can not figure out why the truck won't start. I have fuel pressure, I have spark, I have pulse at the injectors, the injectors test fine, I have changed the coil, I had the ignition module tested and it tested fine, I have checked the ground and all are good, all fuses are good.
The only thing I am iffy on is the voltage at the injectors. I tried testing with a 9v battery originally and got nothing, which lead me to believe that the injectors were bad. But I eventually tested them off of a 12v battery and they will fire fine. When I test the voltage at the injectors off of the harness I am only getting about 9 volts, so if they will not fire when tested with a 9v battery then I would assume that the 9 volts they are getting while cranking the engine is not enough to fire them either. But....where am I losing voltage?
I am about to the point where I am going to order an adapter plate and put a carb on it!

[Chevy3+3]

Are the injectors spraying fuel while you are cranking?

[Chrispbrown36]

No spray. At most there is a drip or two that drop out.

[Chevy3+3]

Ok I'm confused. You said in the above post that the injectors pulse but now you just said they don't spray fuel? Will it still fire and die if you dump fuel down the tbi bores?

[Chrispbrown36]

The injectors will pulse when I run wires directly from the battery to the injectors (one constant, the other just touching intermittently). I changed the ignition control module today and still no change.
It does not fire and die when I dump fuel down the bores anymore. I was really hoping that the ignition module change would work. I have gone back through the harness and checked and replaced any splices that are suspect and still nothing. I also tested the pickup coil and it tests fine.

[Chevy3+3]

Did you remove the distributer? Are you sure you stabbed it back correctly?

[Chrispbrown36]

I did remove the distributor.....a couple hundred times. Every time I run out of things to check I pull the distributor, bump the motor til I feel the suction then the pressure blows my thumb out, and stab it back in there.....still nothing.

[Jake Wade]

If your injectors are not spraying fuel while cranking the engine over, chances are the module in the distributor is bad.

[Chrispbrown36]

Changed it today....no change.

[Chevy3+3]

Have you checked your oil pressure sending unit? Did you accidentally pull the wires off. The oil sending units actually control the engines ability to start in case the engine dies from an accident.

When you stabbed the distributer back on the compression stroke did you make sure the rotor was pointing to the #1 plug wires location on the cap?

I'm pretty sure if your not sending signal to pulse your injectors it's either the ICM which you have replaced or the pick up coil. The pickup coil would actually cause a no fire and no pulse of the injectors.

Also how did you test the pickup coil?

[Chrispbrown36]

I am not 100% sure on the oil sending unit wires, but I will check as soon as I can.
Yes I lined up on the #1 spark plug wire location on the cap.
I tested the the resistance across the two connections on the pickup coil. From what I found it should be between 500 and 1500 ohms of resistance and I had just over 700 ohms, so it should be fine.
I appreciate the help, man. I am pulling my hair out over this....we are having a bonfire for my daughter on Saturday and without the truck we can't get the hay bales and some other things for the party....the worries of a father never end! ha ha

[Chevy3+3]

Check this out. It help another guy I helped get his started. I know some of it wont pertain to you but it definitely covers the ignition system.

http://easyautodiagnostics.com/gm/4....ed-icm-tests-1

His ended up being the center spring loaded post wasn't making contact and therefore not firing. He replaced everything but the distributer cap. A new distributer cap fixed it. So make sure you have 12V at the coil when the key is in the run position. Without that nothing will happen.

[Chrispbrown36]

Well....a new development. Today I test the fuel pressure. I had assumed that because I had fuel at the TB that the pressure was fine. After doing some reading last night that said that might not be the case I decided to test it...6 psi. Not real happy about this since money is tight. Also looks like the truck isn't going to be back up and running for Saturday either.
On an 87, can I remove the bed and access the sending unit or will I have to drop the tank? From what I can see the unit sits pretty darn close to being under the cab. I really don't want to drop the tank with 3/4 of a tank of gas in it. I also don't want to have to replace the tank straps right now and spend more money.

[Chrispbrown36]

Oh....one other thing. I thought it was unusual that the fuel pressure tops out at 6 psi when cranking but when you stop cranking it jumps to 10 psi....is this normal?

[Chevy3+3]

Originally Posted by Chrispbrown36

Oh....one other thing. I thought it was unusual that the fuel pressure tops out at 6 psi when cranking but when you stop cranking it jumps to 10 psi....is this normal?

Just curious but have you changed your fuel filter lately?

I just did both fuel pumps in my truck. It was actually easier to leave the tank straps alone and just unbolt the actual brackets that sit under the tank. Should be 4 bolts through the frame for each bracket. Undo those and the tank will drop straight down.

[Chevy3+3]

I will also add that if you don't have spark or fire yet at your plugs then I would tackle that first. That's your bigger problem right now in my opinion.

[fang508]

If this is a tbi system shouldn't you have about 60lbs primed going to tbi regulator and about 13lbs while running out of the regulator? I rebuilt my tbi with new gaskets and such and a 9v bat made my injectors pulse audibly. Hook a volt meter up to the injector power terminals when you crank and see if they get any voltage. Also, make sure your fuel pump isn't bad you should hear it buzz when you prime it.

[Chrispbrown36]

I tested in front of the fuel filter so a clogged filter isn't at fault...though it probably wouldn't hurt to change it.
I will continue to mess with it and the fuel pump is going to have to wait.