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LMC Truck



Username Post: No start no fuel 92 s10 4.3 tbi        (Topic#347065)
Rockodaniels 
Forum Newbie
Posts: 5

Reg: 09-09-17
09-09-17 02:05 PM - Post#2707191    

I'll start with my original problem and go from there. When I got the truck I had an issue where it would start after long cranking time and would run like a top for as long as I wanted. If I shut it off to go into store or whatever and tried to start again it would not start till after it sat for about an hr.
At this point I was assuming the relay is bad and need to replace and the fuel pump was running off the oil pressure sensor switch. Well before I got around to replacing the relay the truck suddenly died on me and would not start no matter how long it sat. I'm assuming the oil pressure sensor switch has stopped working. So I buy a new relay and still not getting fuel.

I went through and checked my wires to the relay and I have a 12v constant and a 12v signal from ecm/pcm with ignition on with the relay out of the pigtail socket but if I plug the relay in and back probe the pigtail I still get the 12v on the constant but no longer get a 12v signal from ecm/pcm. So I replace the ecm and still no difference. I used a jumper wire from the 12v constant to the wire for the fuel pump and it runs and fires up just fine. At this point I am stuck and don't know what else to do. Do I need to replace the oil pressure sensor switch in order for the relay to work properly?

here is a list of everything I have replaced so far.
Coil pack, icm, ecm, fuel tank, fuel pump, fuel filter and relay.

To give a little back story on the truck, it was stolen at one point before I bought it so the ignition is pulled out leaving an empty socket and the other side of the column is busted up a little revealing the inside. I can post pictures if need be.
Could the ignition switch be my problem? A friend of mine suggested a bad ground so where but I wouldn't even know where to begin on that



 
LMC Trucks
rockfangd 
"4th Year" Gold Supporting Member
Posts: 2276

Age: 31
Loc: Utica ny
Reg: 04-13-10
09-09-17 06:12 PM - Post#2707209    
    In response to Rockodaniels

If you turn the key on without cranking does the fuel pump kick on for a few seconds?
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Rockodaniels 
Forum Newbie
Posts: 5

Reg: 09-09-17
09-09-17 08:23 PM - Post#2707224    
    In response to rockfangd

No, I guess I never specified that the relay does not engage for it to send power to the pump unless I use a jumper wire



 
gchemist 
Senior Chevytalk Moderator
Posts: 24200
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
09-10-17 06:16 AM - Post#2707252    
    In response to Rockodaniels

Welcome to the site.

Did you replace the oil pressure sender? Over time, gunk goes build up inside them causing false readings. Check the connector too. It's probably oily which can cause a bad ground.

Does it start in Neutral? Is it a manual or auto? The neutral safety switch may need an adjustment.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
Rockodaniels 
Forum Newbie
Posts: 5

Reg: 09-09-17
09-10-17 12:30 PM - Post#2707294    
    In response to gchemist

No I haven't yet. Was considering it but didn't know if that would affect the fuel pump relay from engaging



 
gchemist 
Senior Chevytalk Moderator
Posts: 24200
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
09-10-17 12:52 PM - Post#2707298    
    In response to Rockodaniels

Pressure may build up, but injectors won't fire. Send me an email or PM. I'll send you a TBI factory trouble guide.

Does it have any codes?

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


Edited by gchemist on 09-10-17 12:52 PM. Reason for edit: No reason given.

 
Rockodaniels 
Forum Newbie
Posts: 5

Reg: 09-09-17
09-10-17 03:22 PM - Post#2707309    
    In response to gchemist

This would be true if it wasn't for the fact that it runs just fine if I run a jumper wire at the relay plug. Problem is not the injectors it's somewhere at the relay or wiring

I could be wrong though haha

I can't get it anywhere to find out any codes. I'm relatively new to all this. Kinda learning as I go so please bare with me



Edited by Rockodaniels on 09-10-17 03:30 PM. Reason for edit: No reason given.

 
gchemist 
Senior Chevytalk Moderator
Posts: 24200
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
09-10-17 04:31 PM - Post#2707316    
    In response to Rockodaniels

Which prongs are you jumping? The relay needs a signal to fire it. Relays are used to power high amp equipment. ECM usually don't supply 12 volts. It's usually 5 or less. I could be wrong on TBI ECM.

'95 Jimmy SLT (Bought @131,814)
'83 Silverardo XST - ZZ4 powered
'96 GMC Jimmy LS Ret. @236651 miles


 
Rockodaniels 
Forum Newbie
Posts: 5

Reg: 09-09-17
09-10-17 05:49 PM - Post#2707323    
    In response to gchemist

I'm jumping pin 5 to pin 2 which is my power constant to the fuel pump. From what I have read I am supposed to get 12v from my ecm as well as the power constant just that I'm only supposed to get the 12v when I turn the key over, which I do as long as I don't have the relay plugged in or a jumper wire from the ecm relay socket to the fuel pump relay socket. My friend has suggested a bad ground but I'm not exactly sure where the ground would be that I would need to check



 
jktucker92 
Silver Supporting Member
Posts: 108
jktucker92
Reg: 02-05-17
09-11-17 02:25 PM - Post#2707415    
    In response to Rockodaniels

The symptoms sound like you have always had a bad relay or bad wire to the relay from the ECM, or bad ECM. Now, you also have a bad oil pressure switch, or wiring issue. The oil pressure switch is a way for the fuel pump to run even if the ECM isn't commanding it to run. You should hear the fuel pump run for 2 seconds every time you turn the ignition from off to on. if it's not, you have a problem somewhere in the ECM, or the wiring from the ECM to the relay, or the relay itself.
The oil pressure switch will provide power to the fuel pump regardless of what the ECM is commanding. Therefore, even if your relay is bad and ECM is bad, once the engine cranks long enough to build oil pressure, the fuel pump will start running and allow the engine to start.

Attachment: TBI_Fuel_Pump_Wiring.gif (12.33 KB) 9 View(s)






 
LMC Trucks
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