Walbro relief valve mod?

[TR Custom Parts]

Put a Walbro from one of our vendors in the GN last year. This pump can never keep up with 1 to 1 boost reference. Always about 5 lbs lower than it should be. Example, 17 lbs of boost, 43 base setting and I get 53 lbs of fuel pressure. Was told by the vendor that the relief valve is probably opening too soon and to punch it down. Sort of sucks having to drop the tank when the pump should have been good from the get go. A run I did a couple weeks ago I was getting 62-63 lbs at almost 30 lbs of boost. Thankfully alky was making up the difference. Used the good submersible fuel line on the pump with the restriction cut off. Clamped correctly as well. Pressures were verified with PL and a couple different mechanical gauges.

My GN only has 34k on it with unmolested fuel lines, new filter, tried two different regulators with no change.

 

[Jerryl]

Mark,
While not listed in your sig, I am sure you have a HW . . . . . . . Did you verify the grounds?
(Subscribed )

 

[TR Custom Parts]

Racetronix hot wire kit, used their chassis ground setup initially as well as a ground from the corner of the tank to the frame. Just recently put in a dedicated 10 gauge ground right to the battery.

 

[scot w.]

I don't think you should have to be taking a 1yr old pump and punching down the relief valve to make it work properly! A 1yr old pump should still be working properly at this point still, modifying it may cause even more problems and then i'm sure it would be Your fault if it didn't fix the issue.... The DW Fuel pump will solve your problems, I have one in my car for over a year now and like it a lot. Plus the DW pump was tested against the walbro (and several other pumps) by Richard Clark at his facility with great results..

SW.

 

[TR Custom Parts]

Scot, send me a Paypal invoice to trcustomparts@gmail.com !

 

[BEATAV8]

Mark,
With the Racetronix wiring, did it include parts for replacing the wiring on the fuel sender itself? They do have parts available for replacing the wires inside the fuel tank with much better stuff, but not sure if older kits had that included.

I replaced the those wires and picked up 5 psi right away.

 

[TR Custom Parts]

Stock sending unit, if I am going in to the tank again I will use their new sending unit.

 

[bison]

Try pressurizing the regulator and use a teed in boost gauge as you add pressure with the pump on. See if it is 1:1. My guess is it will be.

 

[TR Custom Parts]

Bison, what will that tell me if it goes up 1:1?

 

[BEATAV8]

Stock sending unit, if I am going in to the tank again I will use their new sending unit.

That sounds good. Any hotwire setup is only as good as the weakest link, which is often the sending unit wires inside the tank!

 

[forcefed3.8's]

Sounds like a bad pump. While idleing, start cranking up the fp. It should be able to go 90 to 100 psi. If it gets shakey and stops around 60 to 70, the pump is crap.

 

[salvageV6]

The gauge teed into the pressure line on the regulator will read boost, f.p. pressure gauge will tell f.p.

A setup like this with shop air and an air regulator with gauge works great.

 

[bison]

Bison, what will that tell me if it goes up 1:1?

It will tell you it's not the internal regulator and that your gauge isn't the problem.

 

[TR Custom Parts]

Tried a couple things, screwed down the regulator all the way and pressure was bouncing off the 100 lb mark.

Applied air to the regulator with the car idling and was seeing 75 lbs. Had the regulator on my compressor set to around 30 lbs or so. I am sure I had some leakage as I don't have the fancy Salvage test gauge hanging around. Attached some screen shots. One shows what I was getting at almost 29 lbs of boost chasing a boost control problem.

Other one shows another run with boost under control. I usually shoot for around 22-24 lbs but had the boost controller turned down.

 

[scot w.]

Mark,

I am holding off sending you the PP invoice, maybe with these checks it might be something else... Once it's determined to be the fuel pump for sure I will send an invoice your way if need be..

SW.

 

[TR Custom Parts]

Not sure what else can be going on at this point. Hose to regulator seems fine, zip ties on both ends, stock metal vacuum line pulls a good vacuum. I do have a BOV so will plug vacuum line to that to see if it makes any difference.

 

[jdpolzin]

In your second frame, it looks like your voltage curve is sagging quite a bit while under boost. Do you have a volt booster? You should have max voltage as the RPM's go up. I think you have a short somewhere or a bad alternator/battery.

 

[salvageV6]

You can borrow the test setup any time.

You're only about 5 miles away.

 

[VIN7]

It looks like your a/f is being maintained ok. Post a screenshot of the high boost but replace volts with injector dutycycle. How much more boost do you plan on running?

Mike

 

[jdpolzin]

It looks like your a/f is being maintained ok. Post a screenshot of the high boost but replace volts with injector dutycycle. How much more boost do you plan on running?

Mike

I have a feeling the alky is what is mantaining his A/F ratio. Fuel should be 10psi higher