Hello, all. Does anyone know if a inoperative EFI-type inline fuel pump would constitute a significant flow restriction for another "lift" pump mounted in the fuel tank?? Let me clarify. I've got a 305 TPI with a Vortech that was originally installed by another individual. While poking around my engine compartment, I was shocked to find out that the "helper" inline fuel pump that comes with Vortech's kit was NOT connected to a power source that was "hot in run." LSS, the pump wasn't getting any power, and thus, wasn't running!!! But, seeing as this extra pump is mounted in series with the factory in-tank unit, I surmise that this could be causing some rather annoying problems with the way the car currently runs (blower belt removed). Specifically, I noticed some weird fuel pressure fluctuations with my rail gauge while goosing the throttle under the hood. I believe that the factory fuel pump is OK as I've run some basic diagnostics on it in the very recent past. I suppose I should consider myself lucky, as it's a miracle that the thing didn't lean out under boost at some time in the past and explode!! I just don't know how much a "sleeping" fuel pump would restrict fuel flow. Any input would be greatly appreciated.

 

I can't tell you for sure, but I know I have changed many of those small GM fuel filters that were so clogged you could not blow through them at all and the vehicle had no driveabilty problems.

I could not tell from your description, but were you having drivabilty problems? What were those weird fluctuations you were seeing?

I'm kind of curious on this, because I was thinking about turning my booster pump on with a Hobbs switch when the manifold pressure is low; like when vacuum is less than 5". That way the booster pump is running before the boost comes in, but not at idle or cruise. It is very loud and annoying to me.

 

The only real driveability problem is a slight hesitation on tip-in. I have tried to address every possible cause I knew of, to no avail (using the "fuel, air, or spark" idea).

Basically, the pressure gauge sometimes drops slightly on throttle tip-in, only to rise slightly just after that. Plus, in the past (five years ago plus, ugh) I can recall taking the car up just past 100 mph, and when I get off the throttle, for a split second, it's as if the engine cuts out completely, only to immediately continue running. I had believed (obsessively) that this was somehow related to spark, rather than fuel. But, in a rare "a-ha" type moment, I noticed that the person who did the initial installation (big mistake: LSS I should've done it myself!!!!) had hooked the power feed wire for the secondary pump to the power feed for the windshield washer pump. This is so effing wrong for so many reasons as you already know.

Recently, I added World Castings heads, and a Crane cam, with a new chip. The car has an occasional popping or backfiring on deceleration now. It's not severe, but it dawned on me that all of these things seem to point to a possible restriction in the fuel system. The secondary pump seems like the most likely culprit at this point, as the fuel filter I changed when I did all that work. Seeing as the fuel has to pass through that "dead" pump, in periods of high demand, that's got to be way less than optimal. I know there are people who regularly post on these boards who know way more than me about this. You are probably one of them. Than pretty much describes my "gremlin."

 

Are you familiar with how a vacuum regulator works? The reason I ask is because I think the FP flucuations may be normal. With an agressive cam, your low idle vacuum may be lower than it is just off idle during 'tip-in'. In other words, as you feed in throttle (slowly), the intake manifold vacuum increases (lowering fuel pressure a bit), then as you continue to open the throttle, intake manifold decreases (raising the fuel pressure).

Why not just properly connect the pump and tell us if it fixes your problem

 

Thanks again. That's exactly what I plan to do.....when time permits. This is the worst time of year for that. Not so much because of the weather (I live in coastal southern CA), but just because of the hectic holiday season. Not to mention the fact that I had originally set aside 3 weekends for my upgrades. It took much longer. I'm still recovering from all of the backaches and unpleasant surprises I got along the way.

I doubt that low idle vacuum could be the culprit. My cam is really conservative by pretty much any measure. (Crane 2031???? .429/.452, 204/214 116 LSA) Although your observation about the tip in fuel pressure fluctuation may very well be right. When I do finally get on it, I'll most likely post here to let you and everyone else who is interested know exactly how it went. Anyway, thanks for your time. Every little tidbit helps.

 

I currently have a GN in-tank and ATI's in-line pump, subject to change if necessary with my new setup. In any case, I have the ability to turn either pump off. Interesting results:

1) With only the in-tank pump running, it starts to labor within 60 seconds. Although the fuel pressure is maintained, the pump starts to whine loudly which I believe is a sign that it's laboring.

2) With only the in-line pump running, fuel pressure drops drastically within 15 seconds and the engine dies.

 

Thanks for that info Willie. I guess I could have easily tried that myself too, just never got around to it. How's you TC set-up coming?

 

Thanks for asking! After about 1-1/2 years hiatus (put only 0.2 miles on my fresh engine in this timeframe), I started back on my project about two months ago. I'm ready to go through smog (required) and get my car registered after being off the road for two years. I've been working on tuning my EPROM with my new 749 / $58 setup for the last month. Once I get through this process and comfortable with the normally aspirated part of the tune, I'll be taking the car through smog. After that, I'll be installing my aftermarket serpentine belt drive system which I now have all the correct parts and fittings for, including the factory smog stuff. Then after that, the turbos go on!

Willie

 

Thanks to both of you for your input. Eventually, I'll get this thing sorted out and see if this little theory is correct. Take care.

 

Willie, that’s pretty interesting info…, but it might be pump specific, since I’ve heard similar with a 4th gen LT1 intank and a t-rex inline and where either way it ran, it sounded labored and things got ugly when boost hit.

The whole thing makes me wonder of an example that I posted in my own thread about this (here) where I’ve seen people use a single intank as a lift and 2 bigish inline boost pumps. Having seen some very unhappy mustang blower kits were only the inline was installed and the stock one left I wonder if it works at all…

 

I sumped my stock tank and will run two walbros when the time comes.... Only plan on a T70 so 100 gph @ 60 psi should suffice.
In tank wasn't an option for me.

It's not that hard to mod the sender unit for two pumps.
As long as it will fit through the whole, I'd think you could make it Mark. Last I checked the FP link on my site had the pumps about the cheapest.

 

That’s part of the question, will 2 pumps fit through the hole on a 3rd gen? If they will I’m sure I can make something to hang two, even if it wasn’t easy, that’s not an issue.

Like I said, I’m seriously considering running the stock + a 255L/h pump in there.

I looked at your price list and your other pages and didn’t see a price for a pump. FWIW, digging through my own shop’s distributors’ price lists I think I found a commonly available p/n which is a reboxed GSS340 for significantly cheaper then most even sell them on ebay. I had a friend double check “what’s actually in the box” and I should actually have one in my hands with this morning’s delivery to confirm…

why is an intank not an option? for that matter, what did you do with the exhaust if you sumped the tank?

 

???? It's a 69' fbody.....
The sender is only about 2.5" in dia. so no way 2 will fit.
No tray in the bottom either.

If you look in the links page it says "Walbro fuel pumps"
here
He sells the fittings for inline use too.
No fair comparing in house pricing.....

When I eye balled a 3rd gen tank it looked like 2 would fit.
Might be close.

 

Wooops, missed the ‘69rs in your tagline…

I thought that you were selling them, sorry. Funny, our inhouse price for anything actually labeled as a high flow 255 doesn’t even come close to touching his prices (I’ve been considering trying to setup a dealer account with him because of it), but I ran across one that is intended to be part of something else which conveniently happens to have a GSS340, big filter sock and install harness/bits and pieces for cheap enough that even a cheap bastard like me thinks it’s a good deal.

As far as where I think I’m going with all this… I guess I’ll post in my own thread…

 

The kit ought to have a relay system for supplying power to the adder fuel pump. If it doesnt, then do it yourself. Relay operates on engine on from same source as stock pump and passes power to the pump. BOTH pumps should operate this way. There ought to be an oil pressure (emergency off) switch in the factory chain already and your relay should operate from the same source sending the OK to run as the factory pump. Logical and safe. See your own wiring from factory diagram. If your system has somehow bypassed this oil pressure safety device or it doesnt work right, a new one is about 20 bucks.

Before worrying about any of this trash, remove the tank and replace the in-tank unit with a better aftermarket, quality, one also. Cleaning the tank and replacing the filter will be included. A second filter should be used at the very end to cover what-ever gets through. Replace any and all rubber line with quality stainless stuff, the extra bucks are well worth the investment.

If anyone is going to go spend much of the money to do a job, they ought to spend enough to do it right. I cant imagine even wondering how well the second pump is pulling through an older, perhaps dirty, fuel pump, sock and tank.