TL;DR truck won't start, funny business with the injectors
So, for some time Heather's (gofergurl) 98 GMC Jimmy has had some starting issues. About a year or so ago I changed out the battery, and that helped for a while.
Once winter set in, the issues came back.
I hooked up a fuel pressure gauge and my Snap-On MT2500.
After turning the key on, the fuel pressure would hit about 50+ PSI, then rapdly fall (about 5-8 PSI per second). No troubles were evident on the computer, other than the ECT sensor was reading a bit high.
Throughout most of the winter and early spring, the truck would only have problems starting when it was cold outside (temps above 40 degrees seemed to be agreeable to the truck).
By "problems starting" I mean that you have to crank the engine several times before it starts, and occaisonally when the motor would stumble there would be an odd thump right around where the torque converter would be.
Anyways, several weeks ago I finally had some free time and decided to try changing the fuel filter before trying to acquire a fuel pump. By the time I got done with the filter, my arms were black. There was a lot of nasty crap in that old filter (it was maybe 1-2 years old).
The truck ran pretty good for a week or so, and then started having problems again.
We dropped it off to get it's annual safety inspection about a week or so ago. After it failed for some lighting problems, we went to pick it up. That truck did not want to start at all.
We finally got it home, and I told Heather that she won't be driving it until we fix the starting issue (because I don't want to be burning up starters and batteries).
So, now I have the fuel pressure gauge and the MT2500 hooked back up.
Fuel pressure holds steady at 50 PSI. Alldata says it should be 60-66 PSI or so.
Running the injector balance test on the MT2500, sometimes I can get all 6 injectors to pulse, other times only 5 injectors show up (and when that happens maybe half of them will pulse).
Right now I haven't been able to start the truck (although, I haven't given it much more than a couple crank attempts). It'll start with some ether sprayed into the intake, but it won't continue to run.
All the solenoids read about 11.8-12 ohms, there is continuity between the ECM and injector plug, and the output of the ECM is pulled to ground any time I pulse the injectors through the MT2500 (even when only 5 injectors show up).
An interesting note about the 5 injectors issue... the display reads:
Injector Balance Test
** Injector #1 **
....yadda yadda yadda....
But when only 5 respond to the MT2500 I see:
Injector Balance Test
** Injector #1 **&
Where '&' is actuall four horizontal bars.
I checked in all my manuals, and can't find any reference to what this might mean.
Right now my next plan of action is to pull the upper plenum, disconnect the fuel lines, and try to flush out the lines and clean the injectors. I also plan on disconnecting the return QD and removing the fuel filter to try to flush any crap out of the lines.
Anything else you all can think of to check?
So, for some time Heather's (gofergurl) 98 GMC Jimmy has had some starting issues. About a year or so ago I changed out the battery, and that helped for a while.
Once winter set in, the issues came back.
I hooked up a fuel pressure gauge and my Snap-On MT2500.
After turning the key on, the fuel pressure would hit about 50+ PSI, then rapdly fall (about 5-8 PSI per second). No troubles were evident on the computer, other than the ECT sensor was reading a bit high.
Throughout most of the winter and early spring, the truck would only have problems starting when it was cold outside (temps above 40 degrees seemed to be agreeable to the truck).
By "problems starting" I mean that you have to crank the engine several times before it starts, and occaisonally when the motor would stumble there would be an odd thump right around where the torque converter would be.
Anyways, several weeks ago I finally had some free time and decided to try changing the fuel filter before trying to acquire a fuel pump. By the time I got done with the filter, my arms were black. There was a lot of nasty crap in that old filter (it was maybe 1-2 years old).
The truck ran pretty good for a week or so, and then started having problems again.
We dropped it off to get it's annual safety inspection about a week or so ago. After it failed for some lighting problems, we went to pick it up. That truck did not want to start at all.
We finally got it home, and I told Heather that she won't be driving it until we fix the starting issue (because I don't want to be burning up starters and batteries).
So, now I have the fuel pressure gauge and the MT2500 hooked back up.
Fuel pressure holds steady at 50 PSI. Alldata says it should be 60-66 PSI or so.
Running the injector balance test on the MT2500, sometimes I can get all 6 injectors to pulse, other times only 5 injectors show up (and when that happens maybe half of them will pulse).
Right now I haven't been able to start the truck (although, I haven't given it much more than a couple crank attempts). It'll start with some ether sprayed into the intake, but it won't continue to run.
All the solenoids read about 11.8-12 ohms, there is continuity between the ECM and injector plug, and the output of the ECM is pulled to ground any time I pulse the injectors through the MT2500 (even when only 5 injectors show up).
An interesting note about the 5 injectors issue... the display reads:
Injector Balance Test
** Injector #1 **
....yadda yadda yadda....
But when only 5 respond to the MT2500 I see:
Injector Balance Test
** Injector #1 **&
Where '&' is actuall four horizontal bars.
I checked in all my manuals, and can't find any reference to what this might mean.
Right now my next plan of action is to pull the upper plenum, disconnect the fuel lines, and try to flush out the lines and clean the injectors. I also plan on disconnecting the return QD and removing the fuel filter to try to flush any crap out of the lines.
Anything else you all can think of to check?
Right now all I have is my MT2500 and a fuel pressure gauge.
