Cutting Out At ~14 PSI Boost - Suspect Fuel Pump

Terbro

Has Member
Joined
May 24, 2001
Alright...it's time I get to the bottom of this! I had my motor built by Nick Micale and he told me he installed (and hot wired) a DW300 or 301 (apparently they're the same) fuel pump at the time. But I'm having a very consistent issue with not being able to run above about 14 psi boost.

What happens perfectly *very consistently*, is right about 14 psi boost, it cuts out. Running E85, and initially only having 60 lb injectors, I thought that might be it. So I upgrade to 80 lb injectors, and a new TurboTweek chip to match, designed for up to 25 psi. No change at all...still basically a near totally loss of power at 14 psi. It really feels like it's not getting enough fuel.

I know, I should probably have a scantool, but I do not. If I have a run where I stay below 14 psi, it feels *perfect*, and generates great, smooth power, and the Scanmaster reads around 800-820 O2 MVs. However, if I stayed in it once or twice briefly for a couple seconds through the power loss, and the MVs were dangerously low. As I remember I saw a high 600 and a low 700 once. So now, not only there's no reason to, I let off the moment it happens.

So...in talking with Nick, he thought maybe it was an insufficient ground to the fuel pump. I added a 10-guage ground to the stock ground and it had no effect at all.

At this point, while I can see that the fuel tank straps appear to be in a different location than originally, suggesting the tank was dropped, I'm thinking that he made a mistake and didn't put in a DW300/301 FP.

But that's why I'm writing this thread. Because I'd like some feedback on other possibilities - before I buy another DW301 FP and drop the tank, assuming I need to install one. There's a hell of a lot more power in this motor asking to be unleashed with another 5-6 psi. Well, of course I know I could go higher than that with E85, but at this point, I plan on keeping the car for years, and don't want to stress the motor that much. I'm sure I'll be happy with 21 psi for a while.

So...any suggestions? Again - it runs perfect up until 14 psi, and then - it's flat on its butt. I took it to an 1/8th mile track and raced my buddy last Fall in his stock 2015 Camaro SS (426 hp), and had him by 1-2 car lengths all 4 times we raced. I had it set for ~15 psi, and when it cut out and went flat, I'd back off to ~90% throttle, and the car would take off again.

Last thought: I believe Nick installed a new stock style fuel filter too. Are those okay flow-wise for E85?
 
If nick said he put a 300 in it he did. He only installs DW300 pumps or the walbro 400 in most cars.

The stock fuel filter is ok to use with e85

If you want to verify the pump to make you feel better pull the tank but at this post in time I think your wasting your time

What plugs ans plug gap?

Put a fuel pressure gauge on it and tape it to the window and see what she's doing under boost. .

It's hard to say what it might be without some type of basic scan tool.

Stock MAF?

What's base fuel pressure?

What ignition system?

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With all due respect to Nick, I've had several significant issues with him. I still respect him, but without going into detail, let me suffice to say, giving him all the benefit possible of doubt - at a minimum, he's made several errors and oversights in my build and during the process that I'm quite disappointed in. As a result, it's cost me quite a bit of time and effort to resolve. For "the most part", Nick has resolved them, but as I said, I'm still disappointed. So at this point - I've lost confidence in him, and so definitely *no*, I do agree with you in your statement 'if he says he put a DW300 pump in he did". AND - this issue remains. And it's a significant one. I shipped to the car 800 miles to him, and I'm very suspicious that he and his associate Dennis were aware of this. I asked him to tune it to 18-20 psi for me before I picked it up. They didn't. I picked it up, and it was tuned to 14. After picking it up, trailering it 800 miles back to Colorado, and upping the boost, I discovered this issue. I had 1/2 a dozen minor issues with it immediately upon getting it home, one BIG one, which he resolved (as I mentioned, after a big hassle, to my satisfaction)...but as I said, this issue remains. And I'd say - it's a big one.

These cars are ALL about boost, and I specifically had it built for lots of power, to run on E85 and intended to run lots of boost, and I can't. So needless to say, I'm not happy - at all. But....this post isn't about whining. So I'll try to be done for the moment. I've only spent a few hundred hours in my head trying to manage my disappointment, frustration, and mostly - *unfulfilled expectations*.

Anyway, you reminded me of one very important thing I still need to do - get a real time fuel pressure gauge with a hose long enough for me to monitor the fuel pressure during a WOT run. That'll speak volumes. I've already been through all kinds of fuel pressure testing. My fuel pressure isn't the issue. I've been up and down the range, through 40's and 50+ psi. Nothing phases it. I'm willing to bet $100 when I get a fuel pressure gauge with a hose long enough, it'll drop during WOT.

LT1 3.5" MAF. Stock ignition system. It's been awhile since I've played with the fuel pressure, but believe me...that's not the issue - as I said, I've played with it TONS....it never made any significant difference. That's why I'm next to convinced it's the fuel pump. Unless there's a kink in the fuel rail/line somewhere.

Nick installed new plugs, so I don't know what he put in.

But again, the reason I'm willing to bet it's the pump, is because of the consistency - if it was something like plugs, or the ignition, or MAF...it wouldn't be so cut and dry. This is plain and simple: Runs perfectly up until 14 psi. If I'm at WOT, it won't cut out until all of the boost is gained, because it's the turbo that's pushing the fuel into the motor...the ECM, is monitoring the air flow right? And when it's determining that the flow is more, it delivers more fuel, according the boost, so when it gets to higher boost, it delivers more fuel, but then the pump can't supply it.

That's my simple theory anyway. I have a fuel pressure gauge with a line, but it's only about an 18" hose on it...not long enough to tape to the windshield. And right now I'm broke, so I can't afford longer hosed gauge.
 
All this boo hoo, asking questions, and having NO data to discuss, is beginning to sound like a bitch session.
I'd suggest you get the tools to diagnose the problem, post the results, then look for suggestions/help.
 
I would verify pressure rise with boost, and check spark plug gap. Also make sure the translator is on the proper setting for the chip and mas.
 
All this boo hoo, asking questions, and having NO data to discuss, is beginning to sound like a bitch session.
I'd suggest you get the tools to diagnose the problem, post the results, then look for suggestions/help.

Right. I could've omitted much of the whining. But I promise, that wasn't my intension when creating the thread. It was only when someone mentioned Nick that I got carried away. I want to reiterate that I still respect him generally speaking and am I know he's held in very high regard in the TR Community.

A scantool would definitely be nice. The Scanmaster does tell me the basics, but 1st order of business is to get a long-hose fuel pressure gauge.

So what's a good long-hose FP gauge long enough to tape to the windshield? I used to have a TR that had a hood mounted FP gauge, and a few months back had someone forward me a link to that style kit, but they're pricey (~$200, as I remember)...so skip that.
 
I would verify pressure rise with boost, and check spark plug gap. Also make sure the translator is on the proper setting for the chip and mas.

Will get a FP gauge and do that. I'll spot check a few plugs to confirm. What's the suggested gap on our TR's?

I have confirmed the GEN II is on the proper setting. And I've played with it a bit, and when I change it to another MAF setting, it instantly runs poorly, so it's definitely set correctly.
 
I would think you could put a longer hose on the one you've got somehow.

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I would think you could put a longer hose on the one you've got somehow.

At first, I thought...no, but then I realized you might be right. We've got Whisler Industrial Supply here, and they're awesome with all kinds of hoses. I just got off the phone with him and he's working me up a quote, utilizing the existing gauge I have (with Schrader fitting and gauge) and just replacing w/a longer hose). Yep...he just called back, 3 foot hose - $19.

Thanks for the tip!
 
Will get a FP gauge and do that. I'll spot check a few plugs to confirm. What's the suggested gap on our TR's?

I have confirmed the GEN II is on the proper setting. And I've played with it a bit, and when I change it to another MAF setting, it instantly runs poorly, so it's definitely set correctly.
You should check All plugs, what if you skip over a messed up one? You'll be chasing a ghost until you finally find it.

If it was my car I'd just replace them to rule it out for the $20.
 
Check what plugs are in your motor , are they nonresistor? I put nonresistor plugs into mine and it would act up very consistently at WOT and it has happened to others on here as well. The problem went away with resistor plugs. Also Nick has stated before that he has seen problems with E85 cars having trouble making over 15psi boost with stock ignition , TR6 fixed it. Food for thought. Sam
 
Check what plugs are in your motor , are they nonresistor? I put nonresistor plugs into mine and it would act up very consistently at WOT and it has happened to others on here as well. The problem went away with resistor plugs. Also Nick has stated before that he has seen problems with E85 cars having trouble making over 15psi boost with stock ignition , TR6 fixed it. Food for thought. Sam
There is an issue with the stock ignition amd e85, there is something wrong. I watched John Plog make 8 sec power with a stock ignition and e85, and I have converted 6 cars with stock ignition to e85, up to 29psi and high 9s with no issues.


Tighten the gap to .025.
 
I have not had this problem as I already have a TR6 ignition, but Nick had mentioned that he has seen problems with E85 and stock ignition. Same thing with nonresistor plugs , some have had problems, myself included , others not.
 
Okay, so...I hook up the gauge, and go for a run, filming it, and for the first time - it doesn't do it! No full-on cut out. Convinced it will later, I take the TR on an errand. And it does lose power to some extent. And this is interesting. In comparing the first "good" run's fuel pressure, it stayed fairly steady - around 50 psi. The "errand" run, which I didn't film, I noticed as the boost was building, the fuel pressure also climbed up to around 60, but then dropped to low 40s at the top of the rpm range/~15 psi boost, as I felt the power drop out.

I'm uploading the vid to youtube now. I'll post it once it's complete. And I'll eventually have a good vid of run with the problem...confident of that.

On the other subject - I don't proclaim to be a technical engineer - but I can't imagine how the motor's ignition system could "care"/be influenced by what fuel is being used. Okay, so it's requires more...so what. How many thousands of TR's owners have taken their cars to the track, put in C16, jacked up the boost to 25 psi with the stock ignition without problems? If they're all doing that w/o problems, I should be able to push 14 psi of E85 w/o the ignition having a fit. And I just can't emphasize enough how very often, the phenomenon is like someone turning off the a manual power switch to the fuel pump. I'll check the plugs gap, but I'm betting that's not the problem. This is often like clockwork - 14.0 psi, power OFF., Let off gas a smidge to 90% throttle, power back ON, and the car resumes pulling *hard* (as much as 13 psi could be) and *perfectly* smooth again.

Just trying my best to paint the best picture I can for everybody...
 
Those were suggestions that others have experienced if fuel pressure was not the issue . You definitely have a FP problem !
E85 is tougher to ignite than gas , which correlates directly to the ignition system .
 
I take that back. After closer analysis, I can see that the fuel pressure did drop to 40. But again it didn't cut out in this run:

It's hard to see on youtube, but on my phone, I can pause (or not) and zoom in to get a better look at the gauge. So at 15 seconds into the vid, it's right at 40.
 
Somebody please tell me what a healthy fuel pressure run would look like. As you can see...at idle, I'm at about 52. In this run, as I increased throttle, it climbed high 50's, then as boost maxed at 15, it sharply dropped to 40. What would one want to see that gauge look like, ideally...during a WOT run?
 
Depends on what it was tuned for at base with the vacuum line off the regulator. It should be base pressure + boost. 1:1 rise. So 20 lbs of boost should be base +20 lbs. For example my car has a base pressure vacuum line off at idle of 43 psi. At full boost I see 72 psi of fuel pressure because im at 29 psi boost pressure.

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Depends on what it was tuned for at base with the vacuum line off the regulator. It should be base pressure + boost. 1:1 rise. So 20 lbs of boost should be base +20 lbs. For example my car has a base pressure vacuum line off at idle of 43 psi. At full boost I see 72 psi of fuel pressure because im at 29 psi boost pressure.

Okay, I just checked, and it's 53 with the line off at the FPR (48 with the line on). I know that sounds high, but as I mentioned, I've been through the range, and have definitely had it at 43 with the line off before. I've taken the advice of others on the board to increase it to where it is now...during my troubleshooting attempts in the past. I'm open to bringing it down and do another run to confirm it won't improve anything. Of course, I don't know what the gauge will look like during the run, but I know it had the cutting out problem when I had it set at 43, line off.

But at this point, what's the concensus on my situation? Looks like I've got one confirmation that I've got a confirmed fuel pressure problem.
 
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