spark no consistent gas

[abvgrndsub]

I have a irritating problem with my 1990 Suburban. The truck will run fine and then just die out and I mean dead. I try restarting and it will crank but will not start. Sometimes it will start after about a half hour or so. Here lately it wont start even after that. I have replaced the fuel pump, fuel filter, fuel pump relay and have rebuilt the TBI as well as blow out the fuel lines. After each one of these things being replaced the same problem still exsist. I had somebody turn the ignition while I look to see if the injectors are spitting gas and nothing. I sprayed carb cleaner in the Throttle Body and it started up and after a few sputters it ran just fine. It runs for a few minutes and then dies and has the same problem. If I spray the carb cleaner then it works again. I dont think its the injectors themselves because its hard to believe that they would both go out at the same time every time. I took it to a shop and they checked the computer and it check out ok and there were no codes. They did 350.00 worth of trouble shooting and came up with nothing. I myself check all the wires and couldn't see anything out of the ordinary. I have no idea what else it can be. Anybody have some advice.

 

[Mad-Dog]

The injector gets it's trigger signal from the ECM which in turn gets it's trigger signal from the Hall Effect Sensor (pickup coil) in the distributor (I don't think the '90 has crank fired ignition)...anyway, the sensor tells the ECM to fire the injectors every 45 degrees of crankshaft rotation (makes sense doesn't it..?)
The pickup coil or the module could be causing the problem, both of these components are susceptible to heat and will fail intermittently or totally with age.
If it is Crank fired ignition then i would replace the crank position sensor after checking it...

 

[abvgrndsub]

Thanks, I have been at this for three month now and this is the first thing that makes sense. I will try these suggestions and let you know if that fixes it. Again Thanks.

 

[dyeager535]

If you are buying ignition parts, save yourself time/effort and buy an AC Delco.

gmpartsdirect.com is a good deal even compared to aftermarket modules that I saw at cskauto and naponline.com.

 

[abvgrndsub]

I called around for thes parts you suggested and Im being told that I dont have Crank Position Sensor in the distributor. Do you think just changing the pick up coil will do the trick. Thanks

 

[Mad-Dog]

Uhhhhhh, i didn't know what ignition system u had......the CPS would be down at the front of motor if ya had it.

Changing the p/u coil involves completely disassembling the distributor and requires a roll-pin punch, the module is much simpler and may cure the no-start.

both of these components are susceptible to hot-soak failure so be sure to use insulating grease under the new module.

 

[abvgrndsub]

Thanks for the suggestion. I decided to replace the whole distributor because I had a shop work on the truck and they said that they had put a used distributor on. Since I now think that may have been the core of my problem I replaced the whole thing. I've never stabbed a distributor but I figured the worst I could do was get the timing off so I went ahead and tried it. I think I got it pretty close. After I got it all buttoned up I started the truck and it sounded the best it ever has. I think I have the problem solved. Thanks again.

I want to check my timing but I understand there is some pink wire that needs to be disconnected before using the timing light. Is this true and if so where is this wire located.

 

[Thunder]

Read the white emissions sticker in the front of the engine compartment or on the air cleaner. It tells you exactly what wire to disconnect.
On Blazers it is usually a black and tan wire with a connector on it that sticks out of a thick wire loom on the fire wall next to the big round brake booster.

 

[Mad-Dog]

that's right, if i'm not mistaken that is the ESC (electronic spark control) circuit that must be disabled before setting the initial timing....