ToManyChevys
Newbie
Posts: 6
Loc: Oklahoma USA
Reg: 08-15-24
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08-15-24 01:53 PM - Post#2872751
So I'm breaking in the 700R4 transmission in my 1990 Chevy k 1500 after having it rebuilt and I have a sudden loss in power in the fuel system that left me stuck in the hot sun (110°F) for hours . I checked the fuel pump fuse and it was fine so then I installed a new relay as a means of checking the old one and that didn't solve the problem, while troubleshooting I find I have no power to the fuse at any time although the fusible links in the same area are all in good condition and if I provide a positive power source to the fuse my fuel pump comes on and the vehicle will start but the pump never turns off so clearly I can't just put battery power to that fuse. Anybody run into this before and have an idea of what it might be?
OG
1990 k1500 Silverado 253596.0
1994 k1500 Silverado 289685.4
1994 K2500 Silverado 184259.7
2005 Chevy Trailblazer 226769.4
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bobb
Super Senior Member
Posts: 6856
Loc: paradise
Reg: 09-05-03
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08-17-24 08:59 AM - Post#2872794
In response to ToManyChevys
if it comes down to it you could run the circuit off the oil pressure.
| 70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails. |
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ToManyChevys
Newbie
Posts: 6
Loc: Oklahoma USA
Reg: 08-15-24
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08-17-24 10:23 AM - Post#2872795
In response to bobb
So I found the problem is that a circuit in ECM has been fried and it was caused when the transmission attempted to shift into overdrive I bypassed it and ran it up again and when it hit overdrive it blew the fuse for the ECM. I'm taking the truck to amco and having them inspect the circuit and see if it's faulty on the rebuild
OG
1990 k1500 Silverado 253596.0
1994 k1500 Silverado 289685.4
1994 K2500 Silverado 184259.7
2005 Chevy Trailblazer 226769.4
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bobb
Super Senior Member
Posts: 6856
Loc: paradise
Reg: 09-05-03
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08-18-24 10:00 AM - Post#2872830
In response to ToManyChevys
hard to fry an ecm. i would drop the pan and see if the solenoid wiring is good and check to see if the solenoid is grounded out.
| 70 L camino, grampa engine, g-force 5 spd, road rage suspension. Pray first before all else fails. |
Edited by bobb on 08-18-24 10:00 AM. Reason for edit: No reason given.
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ToManyChevys
Newbie
Posts: 6
Loc: Oklahoma USA
Reg: 08-15-24
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08-24-24 11:44 AM - Post#2873024
In response to ToManyChevys
So Aamco couldn't diagnose the problem and I've noticed that the transmission doesn't remain engaged when I let off the gas or gear down. I can downshift to 2nd and it doesn't attempt to drag/slow down the truck. I've tried to use 4L in 1st to descend a hill slowly but it doesn't hold which left me depending on the brakes and wondering why it seems to go to neutral when you let off the gas but re-engages the gear when you give it gas again.
OG
1990 k1500 Silverado 253596.0
1994 k1500 Silverado 289685.4
1994 K2500 Silverado 184259.7
2005 Chevy Trailblazer 226769.4
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 Shepherd
Valued Contributor
Posts: 3598
Loc: Lake George, NY
Reg: 11-11-15
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08-24-24 12:01 PM - Post#2873026
In response to ToManyChevys
Could be a bad sprag, pretty sure that unit is coming out based on what you described.
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ToManyChevys
Newbie
Posts: 6
Loc: Oklahoma USA
Reg: 08-15-24
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09-25-24 07:34 PM - Post#2874218
In response to ToManyChevys
So I figured I'd give an update, turns out the wiring harness that plugs into the final lock up solenoid was shorted out at the pigtail and that's what caused the fuel system failure in the ECM and yes the ECM will have to be replaced. As for no engine braking I've pulled the transmission back out and taking it back to the shop, unfortunately it was dropped in the shop and now they have to locate a new case because they broke it. Waiting for the call so I can go watch them take it back apart to find out what is wrong with it.
OG
1990 k1500 Silverado 253596.0
1994 k1500 Silverado 289685.4
1994 K2500 Silverado 184259.7
2005 Chevy Trailblazer 226769.4
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