Cutting Out At ~14 PSI Boost - Suspect Fuel Pump

[TurboTnZ06]

I didn't read all that, but, a very similar issue, tune the TT chip via the mid-boost option. I had to set my target a/f differently under mid boost to keep it from breaking up with my very strong wastegate compared to most, right at 12-14 psi at a "light" throttle position. Usually, it is something simple, but you need the proper scan/logging tools to make life somewhat easier. Good luck.

 

[turbo89]

Okay, let me ask if this has any potential to determine flow rate, vs. a *proper* bench flow rate test:

Set up a hose at the end of the fuel rail with a 5-gallon gas can, and jump the pump and run it for 30 seconds. The DW pump is rated to flow 340 liters/hour (I've also seen 320), which is 34 liters/minute, which is 8.97 (call it 9) gallons/minute. If I ran the pump for 30 seconds, *in the car, under those conditions*, (@~5,700 elevation), could I expect to get anything close to 4.5 gallons?

The reason I ask, is if I got a "yes" answer to that, and ran the test and got significantly less, then I could assume I either have a faulty DW pump or don't have a DW pump. I'd then just buy one, and have it at the ready for when I drop the tank!

It will be close enough to tell

 

[JustABuick]

Question: Are the DW300 FPs, known to be much louder than say a Walbro 340 or stock pump? The reason I ask is - last night, when I was doing the test with the return line capped off, the pump didn't sound especially loud. I've heard some loud fuel pumps in my day, and this one wasn't anything like that. It's not a pump that would ever be loud enough to hear if the motor was running. And my SS Pypes exhaust isn't that loud at all. Point being - just wondering again if I've actually got a DW300 pump.

I'm all for dropping the tank and replacing the pump, but maybe I'll inspect the fuel lines further for kinks, replace the FPR first?

And I've been told that there's no practical difference between a DW300 and 301, other than the outer housing - the internals are the same. Is this true?

This probably isn't of any help now, but I recently switched to E85 and went from a Walbro 340 to a DW300, and the DW300 is definitely quieter than the Walbro was.

I am having a similar issue, a cutting out when rolling into the throttle, and I wonder if it's a fuel pressure issue related to stock lines? I didn't see anywhere in your posts if you're running bigger lines or not. i'm still on stock ones.

 

[turbo89]

This probably isn't of any help now, but I recently switched to E85 and went from a Walbro 340 to a DW300, and the DW300 is definitely quieter than the Walbro was.

I am having a similar issue, a cutting out when rolling into the throttle, and I wonder if it's a fuel pressure issue related to stock lines? I didn't see anywhere in your posts if you're running bigger lines or not. i'm still on stock ones.

your not going to run the stock lines out until you are LOWER 10's

 

[JustABuick]

your not going to run the stock lines out until you are LOWER 10's

That's great, because I didn't want to have to run bigger ones. I've just heard some people have fuel pressure problems with stock lines, but I know each car is different. Didn't see if the OP was still running them or not, looks like he has a pretty stout build.

 

[Terbro]

I do have the stock lines. Good to know (at least most) are okay into the 10's. But I'm assuming, aside from a kink in them, at 15 psi, the "stockness" isn't the issue.

 

[joeb1300]

Same problem got so tired of messing with mine buying more crap from Eric shipped car up to jack cotton and he going back to pump gas . good luck brother i know your pain. Watch out don't blow head gasket.

Sent from my LG-LS980 using Tapatalk

 

[turbo89]

Same problem got so tired of messing with mine buying more crap from Eric shipped car up to jack cotton and he going back to pump gas . good luck brother i know your pain. Watch out don't blow head gasket.

Sent from my LG-LS980 using Tapatalk

So what are you trying to say that just because you can't tune that its E85 that's the problem ?

 

[Terbro]

As mentioned BASE + BOOST = correct rise in FP.

Chuck, how is it that the FP rises with boost (or is supposed to)? I'm just curious about the technical aspects of it. I don't understand how increased boost can "get" to the fuel rail and increase the pressure. Is there some ECM programming that I'm unaware of? I just don't see how the fuel delivery system would "know" that boost is present, or be otherwise influenced by it.

 

[turbo89]

Chuck, how is it that the FP rises with boost (or is supposed to)? I'm just curious about the technical aspects of it. I don't understand how increased boost can "get" to the fuel rail and increase the pressure. Is there some ECM programming that I'm unaware of? I just don't see how the fuel delivery system would "know" that boost is present, or be otherwise influenced by it.

Fuel pressure regulator .. when pressure gets applied to it .. it closes off the return to the tank .. mechanical means

 

[larrym]

Boost pressure on the diaphragm increases the spring pressure inside the regulator

 

[Terbro]

Oh yeah...FORGOT about the vacuum line going to it! Bad brain tonight. I was thinking, "It's just a simple mechanical fuel pressure regulator. How's it supposed to know?". Sigh...

 

[turbo89]

Oh yeah...FORGOT about the vacuum line going to it! Bad brain tonight. I was thinking, "It's just a simple mechanical fuel pressure regulator. How's it supposed to know?". Sigh...

yeah sometimes the internal diaphragm can go bad or leak and then there isn't the 1:1 rise of fuel pressure to boost pressure .. same if the pump can't keep up..

just something to check to verify

 

[Terbro]

Okay, so question: Is base pressure adjustment mechanism independent of the spring that increases pressure with boost?

I did adjust up the base pressure to test all the way up to 88 psi, but if boost actuated portion of the FPR is independent, (and broken), that would obviously be the cause.

 

[turbo89]

Okay, so question: Is base pressure adjustment mechanism independent of the spring that increases pressure with boost?

I did adjust up the base pressure to test all the way up to 88 psi, but if boost actuated portion of the FPR is independent, (and broken), that would obviously be the cause.

no the base pressure adjustment mechanism actually TENSIONS that spring .. so when you tighten down the adjuster .. what your doing is putting more tension on the spring causing the fuel pressure to rise. .. then you have the ADDITIVE amount on top of that based on the BOOST PRESSURE via Diaphragm which is added to the spring pressure

Think of it just like a External wastegate that has a adjuster screw on the top and a diaphragm that has boost pressure applied to it

 

[Terbro]

yeah sometimes the internal diaphragm can go bad or leak and then there isn't the 1:1 rise of fuel pressure to boost pressure .. same if the pump can't keep up..

just something to check to verify

You beat me to it (see my last post). Spring or diaphragm? I'd love to check to verify. Is that as simple as disassembling the FPR and inspecting the diaphragm? Attached is a photo. Looks like a few allen screws and I can pop off the housing.

 

[turbo89]

You beat me to it (see my last post). Spring or diaphragm? I'd love to check to verify. Is that as simple as disassembling the FPR and inspecting the diaphragm? Attached is a photo. Looks like a few allen screws and I can pop off the housing.

yupp .. pretty easy to see if its torn

 

[Terbro]

no the base pressure adjustment mechanism actually TENSIONS that spring .. so when you tighten down the adjuster .. what your doing is putting more tension on the spring causing the fuel pressure to rise. .. then you have the ADDITIVE amount on top of that based on the BOOST PRESSURE via Diaphragm which is added to the spring pressure

Think of it just like a External wastegate that has a adjuster screw on the top and a diaphragm that has boost pressure applied to it

Gotcha. So as you said, it's possible it could be the diaphragm. What are they made out of - rubber? If I take off the outer housing of the FPR, will I be able to inspect it and see?

 

[Terbro]

yupp .. pretty easy to see if its torn

Nice. Will do tomorrow.

 

[Terbro]

I just remembered that I noticed that the fuel pressure dropped rapidly (<10 psi in ~2 seconds) after turning off fuel pump.

Do we think that that's somehow a symptom of the problem? And if so, what could cause that to happen?