Hi-
I recently drove the H1 from Seattle to the Jersey Shore. I took my time and did the trip in 11 days stopping at Yellowstone, Badlands, Mt. Rushmore among other attractions. I was towing a 16' trailer which was filled with household goods, a motorcycle and a set of spare tires. The truck did it with a few little hickups. Thirty miles out of Spokane, WA one of the transmission cooling lines burst. I noticed this once I lost overdrive and smelled coolant. I pulled over, took a look at the issues, took the motorcycle out and went to town to get parts. An hour or so later I was back on the road. The next hickup was when i was in the mountains I started to lose power and the engine was running different. I pulled into Jackson Hole and found the nearest Autozone. I spent 6 hours changing out injectors and glow plugs that i had purchased from SSDiesel Supply a week earlier. The difference was great. The final issue is what I write to you experts for.
Towards the end of my journey the truck started having issues starting. I would crank, crank, and crank. Roughly 10 seconds would go by before the truck would come back to life. Once it was running it was not stoppable. One thing to note: previous owner has relocated the lift pump to closer to the tank and swapped it out for a cummins type. I re-traced the system and noticed that there are no check valves in the fuel supply lines. I believe that the lift pump has one built in which might be failing. My intentions are to put the truck back to it's original specs. I wright to you for some information regarding these check valves.

What size are they?
Is there a part number?
An alternative part?
What size are the supply and return lines (mm or in)?
A wiring diagram for the fuel system?
Is there a pressure regulating valve? If so, a part number?

Any help would be greatly appreciated.

1995 Hummer H1 6.5 NA
95k New IP, Injectors, glow plugs, glow plug controller,

-Pavel

 

there are two valves where the two metal lines come off the tank. the metal linesstip and a rubber hose is installed and the valves after that. there is a feed line vent and a return line vent.
part # 12342953-1
and # 12342953-3
AM General part only that i know of.iam sure you could fit any fuel check vales in the same spots.

 

Speaking of fuel systems, My 2002 H1 (I've had it 5 weeks-70,000 miles on the odometer) has died on me about 3-4 times for some unknown reason. Fortunately, it starts right up. It's had good service records, and the last LOF change was less than 2000 miles ago. Could this be the fuel system? Fuel filter? Pump? Where do I start to look???
This morning, the tranny started shifting erratically.
Any ideas???

 

djdadds -
With the symptoms you have listed the fuel system would be a good place to start. I am not 100% on setup on the '02 but check the fuel filter and see if it is dirty. If that all checks out, check to see if your lift pump is running when the truck is running. A non-running lift pump could be the result of a bad relay or a pressure switch. However, I am not sure how the electrical is setup on your truck. Regarding the transmission, you will need to pull some codes to see what it says. If you are low/high on fluid it will act up. On my truck, I can short out two pins on the OBDII port and pull codes via transmission light. Some good info here: Hummer Transmission Information
Let us know what you find out.

-Pavel
'95 Hummer H1 6.5 NA

 

Some information on troubleshooting the lift pump:
Trouble Shooting the Lift Pump

-Pavel
'95 Hummer H1 6.5 NA

 

Thanks, Pavel...
I hope I don't have to pull the doghouse apart to change the lift pump any time in the future. I'm in the process of damping and insulating for sound reduction, which includes taking it apart down to the metal. Lots of cables, etc., to mess with. Maybe I should do it just because I'm in the area! Is there another way to access it that's easier?
Speaking of OBD scanners, do you recommend a good one?

 

You should be able to access the lift pump from the engine compartment. Its on the driver side by the fuel filter. It will be a tight working area. Removing the doghouse and getting to the rear of the engine takes me no longer than 15 minutes. After a few times you will be pretty good at it.
As far as the OBDII scanners go I don't have a good recommendation as I use the TECH 1 tool. This is the scanning tool that GM uses. If I am correct, you could go to an auto store like Autozone and use theirs for free. If not you could always use the Field Service Mode:

"FIELD SERVICE MODE

You can read fault codes without any service tool if you short pins 5 and 6 of that connector. When pins 5-6 shorted check trans lamp gives the code with flash sequence. First comes 12 and then possible fault code. Codes are shown in sequence. E.g..12 is flash, pause, flash, flash, long pause and same again. Be careful playing with connector.

Connector pin order is:

from left upper corner: 1=np, 2=?, 3= np, 4=chassis ground, 5=signal ground, 6=enable PCM diagnostics, 7=np, 8= np

from left lower corner: 9=serial data, 10=np, 11=np, 12=np, 13=np, 14=np, 15=np, 16=unswitched battery 12V np = no pin at the connector" Hummer Transmission Information

Hope that helps,
-Pavel

 

Thanks, Pavel,
I can't imagine getting the doghouse apart in 15 min., but I guess with enough practice...
I've got around 70,000 miles on the engine. Would you think it would be a good idea to just change the pump and the filter, now that I've got the doghouse plastic cover off--with all the cables, electronics, etc. dangling all over the front of the drivers's area? I'm remembering that there are two straps/clasps and maybe a few bolts that hold the doghouse in place. I've since covered everything with RaaMat and Ensolite, though it wouldn't be hard to uncover them. Anything else that I should change while I'm there? I don't want to do this on a regular basis!
I'll check out the OBDII TECH 1, if it's practical to buy one...

 

It's very unpractical to buy a Tech 1 as they are very expensive. I just lucked out on a guy that had one sitting around in his shop. I don't recommend changing the lift pump unless there is something wrong with it. Once the doghouse is off and you have access to rear of the engine I would test the pump electrically and mechanically. Start the truck, its going to be loud inside, and listen to it and if possible measure the voltage. Stop by an AutoZone and pick up a fuel pressure test kit. Its on their FREE RENTALS list. You will pay a deposit at first and get it back once the tool is returned. Hook it up on the discharge side of the pump and check your discharge pressure when the truck is running.
Change your filter since you are already back there.
Where are you located?
Let us know what your progress is.
Is there an email that I can contact you at?

 

Pavel,
I just sent you a PM with my email. I decided not to access the engine through the doghouse; the mess associated with the wires, plus Raamat and Ensolite make it look quite cumbersome. I'll try the access from the engine compartment to see how that goes...