Good luck and keep us posted.

 

I checked a snapshot of PIDs I took of my H3, and you're correct, only a handful parameters are available on OBDII port; fuel pressure is not one of them. I looked a mode 6 and it does not have anything to do with fuel pressure either. Manufacturer specific PIDs (Mode 22) may have it, but I don't have the description of how to get to it.

In any ways, good luck!

Thank you.

 

is f p not avail on SOME h3? it shows on my scanguage 2 in my h3 10

 

@drtom
I think it'd be helpful to know the fuel pressure value at different RPM. It would help OP to troubleshoot the fuel pump "weakness".

Thank you.

 

mine reads 43 always. the book says the pump supplies constant pressure with a regulator built in the assembly.,,,with a FUEL FILTER!!,that everyone says the h3 does not have!

oh,43? pounds i guess

 

I replaced the fuel pump about 2 weeks ago as planned. That process wasn't too bad actually. It took about 2.5 hours to do in my driveway. I will post my own simple instructions for future use since I was unable to find this on the internet.

1. Drop the tank skid plate (4 bolts)
2. Remove the two lines near the front and back of the tank (aluminum fuel delivery line out front and evap line out back - you will need special quick connect fuel line fitting removal tools)
3. Drop the tank slowly with a jack (2 bolts)
4. During or before the the drop, remove the rubber fill line (hose clamp attachment)
5. During the drop, disconnect the wires on top of the fuel pump
6. Drop the rear of the tank down to the ground and pull rearward until the front drops off of the crossmember. (this step required me to jack the truck up a bit (33" tires not quite tall enough)
7. Pull tank out from under the vehicle and start removing pump (counter clockwise. The top of my pump was very rusty and required some convincing to get off of the tank (I used PB blast a hammer and flathead screwdriver).
8. Once pump is loose, disconnect the return line mounted to the pump (inside the tank)

All the installation steps should be self explanatory.

 

I replaced the fuel pump 2 weeks ago. The car ran fine for 2 weeks. (I drove it the entire time to eliminate the possibility of my wife being stranded). Now on my way home from work the other day, it just stalled out on my dirt road. Gladly I was able to coast it down the 1/4 mile stretch of dirt road that leads to my house.

The symptoms are the same as previously, the motor cranks over, but I have zero fuel pressure (I finally bought a gauge with the right fittings).

So now after a bit of review, I am thinking I have a grounded wire somewhere. I did a continuity check from the right side of the fuel pump fuse connection to ground. This should have read some measurable number of ohms (maybe 4-10 ohms). The meter immediately went to 0.00 ohms and steady. Note: Of course this was done with the fuse pulled.

So what I need to do now is just find this short. I think the most convenient way would be to remove the power connector on top of the fuel pump and see it the short stays in (zero ohms). The tight spaces on top of that tank will require me to drop the tank to access. The problem is as soon as I pull the tank down again, the short may go away due to disturbing the wires. One thing I want to make sure is that the fused connection goes directly to the fuel pump and not through the fuel pump relay or anything else. I bought an electronic manual for this on ebay, but I may have to get some assistance deciphering the 119 page electrical wiring diagram. If anybody has any insight on where to start looking for this short or if I am looking at it all wrong it would be appreciated.

Also, 2 more questions:
If there is a short in the fuel pump wiring, why wouldn't that blow the 15A fuel pump fuse?
Is the right side of this fuse supposed to be grounded? (seems kind of unlikely, but this would throw my whole shorted wire theory off)

 

The low Ohm reading is likely due to reading through the fuel pump motor to ground. Check the resistance (Ohms) across the fuel pump you removed to see if it is close to zero Ohms. May want to check or replace the fuel pump relay. I have experienced relays that would drop out after a while. The relay should be less than $20.00 at an auto parts store.

If you had a hard short to ground it would blow the fuse or eventually melt the wire.

Is there any pattern when this happens? For example, going around sharp turns, driving on rough roads and so on.

 

@timfoster
I checked the relay, by swapping it with the one for the wiper motor (identical). The wipers worked fine in all modes with both relays. My fuel pressure however did not change with the other relay.

 

Sorry it has taken so long to update this. Fixing this truck went on the backburner for a bit because I finally purchased a 3rd car. I have been doing a few things to the car (struts, brakes, rotors, etc...) to get it to the point where I am comfortable with it as a daily driver. Now that I have this car fixed up, I will have some time to work on the H3. I plan to partially drop the fuel tank this week to disconnect the pump and check for a ground in the wire. I would like to just find the spot of wire that is grounded and repair it. However, if I can't find it, I may just have to run my own wire.

I am still not 100% confident that this is the issue, but after reviewing the wiring diagrams (in-conclusive), this is my next step.

See copied text from a past update of mine which describes this unresolved question:
One thing I want to make sure is that the fused connection goes directly to the fuel pump and not through the fuel pump relay or anything else. I bought an electronic manual for this on ebay, but I may have to get some assistance deciphering the 119 page electrical wiring diagram. If anybody has any insight on where to start looking for this short or if I am looking at it all wrong it would be appreciated.