Im in my H1 at the side of the road. My engine just died in traffic and I had enough momentum to get off the road. My 20 amp fuse for the ecm/lift pump blew. I replaced it and the truck started, fuel pressure was good, it ran for 30 seconds and blew the fuse again. If i replace the fuse again it will make fuel pressure, start and pops the fuse again...Its a little hard to think and im pouring through the forum looking for suggestions but an up front advice string would be nice. Yes my spare pmd and pmd extension are at home on the shelf.......Sandy.
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Help. Dead at roadside. 20Amp lift pump ecm fuse blows
- Thread starter Sand
- Start date
jrsavoie
Recruit
Is it the same fuse for the ECM and lift pump?
If so, can you unplug the lift pump and see what happens?
If it is the lift pump and not a spot on the harness causing the fuse to blow, you might be able to start and run without the lift pump.
Do you have a lift pump jumper installed? I have a fused toggle switch on all of my 6.5's to run the lift pump whenever I so desire. Such as when I am changing the fuel filter and want to prime it
If so, can you unplug the lift pump and see what happens?
If it is the lift pump and not a spot on the harness causing the fuse to blow, you might be able to start and run without the lift pump.
Do you have a lift pump jumper installed? I have a fused toggle switch on all of my 6.5's to run the lift pump whenever I so desire. Such as when I am changing the fuel filter and want to prime it
ak diesel driver
6.5 driver
Try unplugging the fuel heater on the FFM
Im back at lunch with my truck. Unplugged both the connectors that come from the bottom of the fuel filter. Im assuming one is water in fuel sensor and the other is the heater? Starts. It idles fine then pops the fuse as shift into drive and start to move. I did manage to move it from the road to Starbucks with 3 fuses. Have I unplugged the right wires? I actually hope I did not snd its just that easy....
I just ran a calculation that suggests I can make it the 11km home with 3700 20A fuses. If each one is in a cubic inch box thats only a little over 2 cubic feet of fuses. I am also searching the threads to find my own answer to my "did I unplug the right wires" query. Thanks again in advance.
Unplugged the lift pump and its running. Drove at slow speed around the parking lot. Still running. Im assuming the toll on my injector pump is not worth limping home at low RPM. Whats my diagnostic from here? Replace lift pump? Its putting out good pressure. The wires to where it heads into the loom look good. Connecters are clean with no broken pins. Wire power directly to the lift pump to get home?
Will L.
Well-Known Member
Yes the 2 under the ffm were correct. Also try the lift pump. If yours is in the factory location, it is next to the ffm underneath the windsheild. 2 wire connection.
jrsavoie
Recruit
I don't know where the lift pump is on a HUmmer. If it's easily accessible I'd just change the lift pump and see what happens.
I'd still install a fused toggle switch to the lift pump for the future.
ak diesel driver
6.5 driver
I wouldn't worry about driving it home without the LP running. It won't cause instant damage like on other diesels, some have driven for months without ever knowing
Twisted Steel Performance
Anything worth doing is worth overdoing.
If unpluging the LP let it run & not blow a fuse then it would seen there is a short in the wiring OR a bad LP... I think a new LP is in order...
Will L.
Well-Known Member
Yes, his does- lift pump through the ops just like a pickup, same parts.
On 93-2004 hummers the ffm is next to the master cylinder, and next to that is the lp. The engine compartment is similar to a van where there is a dog house. Center of the engine is almost center of the windshield.
On hummers 1996 and newer, the engine and trans is set up basically the same as trucks.
(93-95 like mine have db2 and no turbo 6.5)
On 93-2004 hummers the ffm is next to the master cylinder, and next to that is the lp. The engine compartment is similar to a van where there is a dog house. Center of the engine is almost center of the windshield.
On hummers 1996 and newer, the engine and trans is set up basically the same as trucks.
(93-95 like mine have db2 and no turbo 6.5)
jrsavoie
Recruit
Do Hummers have issues at the heater blower like the 6.5's do?
Could there be melted wires there?
IS there a heavy draw from the battery with the key in the run position?
What all is on that fuse?
How are your volts reading when all this is going on? Do you have an amp gauge?
So here was my get home plan. 20amp breaker taped to the dash with aligator clips. I put some solder on the stripped ends of the wires and slid them into the fuse block. Strangest thing. Not a blip of trouble all the way home. Didn't trip once. This leads me to think I may have an issue at the fuse holder. Weak tab or something. Ill check it closer in the daylight tomorrow.
Attachments
Will L.
Well-Known Member
@jrsavoie
Yes to the heater blowers. Hummers use gm a/c and heater componets except the radiator,evaporator, condensor, and heater core. I am not sure on the blower motor itself, but the electrical to them is the same. Iirc they dont go exact year for year though, more below, and i never pay attention to interior control units in my trucks to recognize -oh, same as my 96 1/2 was, etc.
For the rest of the circuit, a schematic is needed- they alter by year. I think the tank selector valve is on the circuit and could be the draw. I know Sand has a manual with schematic, and is looking into it when he gets free later.
Sidetrack about the hummer why Sand's 97.5 hummer is far more desireable than 97 or older hummer:
The evaporator/ heatercore in many 92-97 get updated to 97.5 year because poor performance and friction issues, quickly identified by the head unit.
http://www.flashoffroad.com/Maintenance/hvac/hvacproblems.htm
For 92-97 owners there was a kit to upgrade and solve many of the problems- like my 95 even when working perfectly performs moderately at best over 100* temps. And for guys in colder climates the heater performance is way better too. But the kits are all gone. I hope to go over the component list soon, and id what parts are still available and what junkyard parts would be needed. I havent chased it because there just isnt many trucks in junkyards in vegas area- 1 place specializing in it, an other yards only get a few trucks here and there. Might be some of you guys that live in areas with lots of chevy trucks in yards could make some extra $ selling some of the old components on the newer versions maybe, idk yet.
Yes to the heater blowers. Hummers use gm a/c and heater componets except the radiator,evaporator, condensor, and heater core. I am not sure on the blower motor itself, but the electrical to them is the same. Iirc they dont go exact year for year though, more below, and i never pay attention to interior control units in my trucks to recognize -oh, same as my 96 1/2 was, etc.
For the rest of the circuit, a schematic is needed- they alter by year. I think the tank selector valve is on the circuit and could be the draw. I know Sand has a manual with schematic, and is looking into it when he gets free later.
Sidetrack about the hummer why Sand's 97.5 hummer is far more desireable than 97 or older hummer:
The evaporator/ heatercore in many 92-97 get updated to 97.5 year because poor performance and friction issues, quickly identified by the head unit.
http://www.flashoffroad.com/Maintenance/hvac/hvacproblems.htm
For 92-97 owners there was a kit to upgrade and solve many of the problems- like my 95 even when working perfectly performs moderately at best over 100* temps. And for guys in colder climates the heater performance is way better too. But the kits are all gone. I hope to go over the component list soon, and id what parts are still available and what junkyard parts would be needed. I havent chased it because there just isnt many trucks in junkyards in vegas area- 1 place specializing in it, an other yards only get a few trucks here and there. Might be some of you guys that live in areas with lots of chevy trucks in yards could make some extra $ selling some of the old components on the newer versions maybe, idk yet.
JayTheCPA
Well-Known Member
A dying LP will eat fuses even though it is still making good pressure. As already mentioned, the IP can go for a long time without the LP, but commentary is that this will gradually shorten the IP's life.
And for verification, is the LP / PCM using the *same* fuse? Or does the H1 have them on different fuses and *both* are blowing at the same time?
And for verification, is the LP / PCM using the *same* fuse? Or does the H1 have them on different fuses and *both* are blowing at the same time?
Hummer uses the same fuse. I supplied my own circuit to the lift pump to isolate it, while having the fuel heater disconnected and the fuse still popped. Im giving the lift pump the OK. The other hidden thing on the circuit is the fuel tank selector. Check out the diagram.
Attachments
Theres a flowchart in the diagnostics section. Im at step 3 i believe
1. Checked - no codes
2. I feel I've ruled oug my Lift pump. Unless some one sees otherwise.
3. When I pull the fuel tank selector switch and check as instructed I read 8.4ohms. Wayyyy to high. The diective for what to do is esoteric. What is the IP ground stud? My first check is there to look for corrosion, mostly broken wire etc. Any ideas what IP stud means or anything missed in my diagnostic?
1. Checked - no codes
2. I feel I've ruled oug my Lift pump. Unless some one sees otherwise.
3. When I pull the fuel tank selector switch and check as instructed I read 8.4ohms. Wayyyy to high. The diective for what to do is esoteric. What is the IP ground stud? My first check is there to look for corrosion, mostly broken wire etc. Any ideas what IP stud means or anything missed in my diagnostic?
