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Won't Run

J

jor

Registered Member
Joined
Feb 19, 2007
Posts
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Location
Tucson
87 Suburban 5.7L TBI

I was out doing some 4-wheeling the other day and really enjoying this old Suburban. It was running and performing great. Anyhow, on the way out of the area I stopped to get back into 2WD. As I reached down to move the selection lever the engine kind of chugged and quit. From then on, it would turn over, try to start but would not keep running. I'm looking for some ideas on how to proceed.

I believe it is a fuel delivery issue. Yesterday, I disconnected the fuel line and turned the engine over - lots of fuel into my glass container. I removed the filter and determined that it does not restrict flow. Finally, I poured a little gas directly into the carb - it started right up and ran for a few seconds until the fuel was gone.

Just looking for some ideas on how to proceed while I look for my book on this thing. Thanks.
jor
 
Check that the injectors are pulsed when the engine is cranking. Need to use a "noid" light (bulb with a + and - lead on it) on the injector connector and watch for it to blink as the engine turns over. My guess is that they aren't being pulsed, which would lead us to figure that the ignition is the culprit, likely the module based on how often no start conditions are attributed to it, especially since when fuel is present the engine runs, meaning it has spark.
 
Thanks for the idea but that wasn't it. Both injectors are pulsing. It starts but then immediately dies. I checked the injectors by watching them while cranking with ignition on:
* injectors disconnected = no spray
* connected = both spraying
* both pulsing (12 volt test light)

I checked that the fuel pump is coming on (2 seconds when key is turned to on). I'm having a hard time figuring this one out. If I pour gas down the throats it will run. Ordinarily, I would say that would indicate a fuel pump issue but I can hear it go on and I can see the spray coming out of both injectors!
jor
 
grab a can of carb cleaner, and see if you can keep it running longer then a few seconds, to make sure it isn't just something else.

where at in Tucson are you?
 
My guess is one of two things, either a really bad vacuum leak or a bad fuel pressure regulator. You can have all the fuel you want but if there isn't sufficient pressure it won't start.
 
Just because you can hear the fuel pump run does not mean it is putting out enough pressure to keep the engine running.
Best thing is to check the fuel pressure down stream of the filter. Should be at least 9 PSI.
My bet it is the fuel pump.
Just went thru this exact same thing with a frends yukon last weekend. truck sputtered and died. Could hear the FP run. Truck would start and run for a few seconds and die. Checked fuel filter it was good. Put guage on it fuel pressure was way low.
Changed FP. Good as new.
 
Thanks to all for your input. I'm having connectivity issues too (when it rains...) and haven't been able to post. Comcast is coming out today to fix it (must be the low man on the totem pole to work on Thanksgiving!). Not sure if this will post but...

Dyeager: I'm not really sure about the spray pattern as I've never seen it before while just cranking. Thanks for the jpg.

Jason: Carb cleaner? I know that if I continue pouring in gas it will keep running. I'm on the NW side (Ina & La Cholla)

4X4high: I haven't been able to find any vacuum leaks. Where is the fuel pressure regulator on this thing?

Thunder: Yea, I'm thinking the same thing now. It must be the pump or the pressure regulator.

Well, I rugged up a pressure gauge. Not sure I did it right but I installed it on the outlet side of the fuel filter. (just disconnected the fuel line and terminated the line at the gauge). When I turn on the ignition, it reads only 1 psi and when cranking it doesn't even hit 3! If I have this rigged right, I guess this points to the pump or regulator.
jor
 
If you just put the gauge on the line, without it going through the gauge,(i.e. Not a T) then it is the pump, or the hose that feeds the pump. Because that would take the regulator out of the system.

I'm leaving for tucson in 5 minutes, My parents live at Orange Grove/ La Cholla, if you need a quick hand lemme know.
 
Thanks to all. I'm going to recheck the fuel pressure again today. Then I guess it will likely be fuel pump time.
jor
 
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