Hey all my name is Scott and I'm new here to the site. I'm having a problem with my 88 full size jimmy and I'm stumped. My truck will start up and run great then suddly will die but both injectors on the throttlebody will keep spraying fuel like the throttle is opened all the way. This issue just pops up randomly and happened a couple months ago I ended up replacing the ICM but problem still was there then i replaced the coolant temp sensor and cleaning the grounds and problem went away. How having problem again. I replaced the CTS again to see if that was the problem but it continues to die with injectors dumping fuel in to the throttle Body. Any help would be greatly appreciated.
CK5
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88 Jimmy Ignition issues
- Thread starter soverton
- Start date
You getting spark when this happens?
Need to google "testing GM HEI" and run through those tests. Pretty easy with a multimeter. With an intermittent like this testing will be difficult, however checking spark will be quick and easy.
Need to google "testing GM HEI" and run through those tests. Pretty easy with a multimeter. With an intermittent like this testing will be difficult, however checking spark will be quick and easy.
4xcrazy
3/4 ton status
I had one injector dump fuel once, it was bad. Never seen them both do it at the same time though.
Yes I do have spark. Very strong. Something else I noticed is that after it dies on me and I turn key off and back on to restart is that the injectors are not shutting of after initial prime like they should. They just continue to dump fuel.
Odd that they continue to dump fuel. Only things that can cause that would be bad injectors (leaking), short to ground on injectors, or an ECM/PROM issue. I suppose there could be an ignition circuit issue indicating to the ECM the engine is cranking, but if the fuel is dumping but not pulsing, that's not it.
I'd unplug them and see if it keeps happening.
Since it does it key on/engine off, may be a short to ground.
Since it does it key on/engine off, may be a short to ground.
so just unplug at each injector? The other problem is I only dose this some times. After it dies and loads up with fuel if I let it set an hr or so it will fire back up run rough till extra fuel burns off then run fine for 3 or 4 min then die and load up on fuel again. Thanks for the replys I APPRECIATE it. I do all my own work on my rig and usually fix or diagnose what is going on but I'm lost this time
4xcrazy
3/4 ton status
If I remember right, I believe I unplugged one injector at a time to determine which one was bad, it's been awhile though but I know I did figure it only being one bad injector, but oddly when it went bad it was causing both injectors to dump when I turned the key on for the initial pump pressure prime.
Being intermittent, it may be hard to unplug the injectors to test. Not sure how else you can do it, if you have time to get in there and remove the air cleaner and see this going on, probably enough time to disconnect the injectors. Just have to be prepared I suppose. Once the air cleaner is off though, you'll know if you need to keep going.
You've checked the injector wires real good to make sure they aren't pinched?
I had a couple bad injectors on my rig (out of 8) and I suspect they were somehow overloading the ECM...start up cold no problem. If it was ever shut off, it would not restart for hours until it was fully cool. So I can see an injector issue causing problems here too, just need to do more work to figure out what is the problem.
I don't know what the spec is for the TBI injectors, but I'm assuming if you google it, you may find the spec for them. It will be given in ohms. That's not a fail proof test, but if they are bad at rest, they are bad. Intermittents normally aren't that easy to find though.
You've checked the injector wires real good to make sure they aren't pinched?
I had a couple bad injectors on my rig (out of 8) and I suspect they were somehow overloading the ECM...start up cold no problem. If it was ever shut off, it would not restart for hours until it was fully cool. So I can see an injector issue causing problems here too, just need to do more work to figure out what is the problem.
I don't know what the spec is for the TBI injectors, but I'm assuming if you google it, you may find the spec for them. It will be given in ohms. That's not a fail proof test, but if they are bad at rest, they are bad. Intermittents normally aren't that easy to find though.
something is telling the injectors to open up. I unhooked one injector and started truck. Ran fine for about 5 min then stalled and that injector opened up spraying fuel. I unhooked that injector and rehooked other injector up with same results ran fine for 5 min then stall and injector opens up. I unhooked both injectors and turned key to on the second I hook up either injector bam wide open fuel dumping into bowl. That is what leads me to believe something is sending a false signal to dump fuel. Also as I watched the injectors put fuel into the throttle body while it was running it wasn't really a spray it was small droplets. Dont know if that's a sign of anything by thought it might be worth mentioning.
4xcrazy
3/4 ton status
Remove the module in the distributor and go have it tested.
Heck, should be able to disconnect the distributor plugs and figure it out without removing the module since this problem seems pretty consistent now.
If the fuel pump is running continuously with the key on/engine off, something is up with the wiring.
If the fuel pump is running continuously with the key on/engine off, something is up with the wiring.
Check your lines to your MAP sensor, or map sensor itself. Best would be to use an ALDL cable and use tunerpro rt(free) to see what your sensors are doing at the time of trouble. I had the same issue as you. Replaced CTS, New o2, regrounded everything and it still came back randomly. Turned out to be a cracked MAP sensor when it got warm it would open up. I knew that because my map sensor suddenly jumped to 96kpa. Worth a check.
