So here's the reason I'm asking; I've got MPFI on my v6, which is close to the V8 TPI's. I've replaced the fuel pump twice so far- not fun. I'm going to be replacing the quarter panel on my car soon, and I'm going to have to drop the gas tank. (The junkyard cut a 1/3 of a Firebird off for me, so instead of screwing around with spot welds, I'll just weld that back half on.)

Someone, I can't remember who, found out that the only difference between the MPFI v6 pump and the TPI 350 pump is flow- the 350 pump flows more. Since I've been thru two fuel pumps already, and they were both Borg Warner (had a lifetime warranty, got the 2nd for free), I'm thinking of replacing the fuel pump for the third time, just for the hell of it, with an AC/Delco pump.

I might be adding nitrous in the future, but until then, I've got an engine to rebuild and a trans to rebuild and fix my 3.73/busted posi/disc axle and paint my car. (whew) But now seems like a damned good time to put a higher flow pump in, in prep for the nitrous system.

So ignoring I've got a V6... what about you guys with close-to-stock TPI's? What if, say, you put the Walbro pump in, but you were still running stock injectors. Does the higher-flow pump mind? Does it burn out? Do you guys run richer? I'd think since the injectors would be unchanged, that the car would still run fine, and any extra fuel would be returned to the tank via the return line from the pressure regulator. But I'd hate to swap pumps "just because I've got the tank out", put a higher-flow V8 pump in, and have ANOTHER pump die on me, OR, have my car run like crap for the next 5 years. If I had to drop the tank again I think I'd take up drinking.

All ideas/opinions appreciated! Thank you!

 

From what I understand, it should not make a difference, even with a V6. Lots of people are running high flow units with stock injectors. What you'll need to look into is the AFPR, that will be the determining factor. At least from what I understand.

See with the stock FPR, it doesn't matter if you have a stock pump or a high flow pump, your still only going to get a certain amount of fuel. With adjusted pressure, your getting just that, pressure. You might be getting more fuel but I'm not too clear on that.

Hope that helps.
Eric

 

If you run much too large of a pump, you can heat up the fuel which isnt a good thing. Thats usually reserved for pumps setup for supplying 1000hp engines Dont think you'll have any problems with a stock TPI pump though, it'll just bypass the rails via the FPR, and it couldnt really flow all that much more than whats in there now. Only thing you might want to look at is the return line, yours might be 1/4 and I think the TPI is 5/16. I never sat down to figure how big the return line should be, but I'd imagine GM did and that number they used is a good enough number for us.

 

Thanks for the replies, guys! So as long as I keep the stock FPR and injectors, I won't get any driveability issues... cool, that's what I was hoping for. And yeah, I'd be happy to get 200 HP out of my 135 hp v6.. those must be some huge pumps for 1000 HP! I wish I could find that old message about MPFI V6 vs TPI V8 flow #s for the pumps, but I think it's too old and was erased, damn. Either that or I'm searching for the wrong things.

Madmax, good point about the return line. Think I could measure the outside with calipers? I do have the '86 GM Service Manual, I wonder if it's mentioned. Aw, hell, if diameter is different, I'd have to replace that whole steel pipe?! Ouch. Or do you think it's just the rubber line that's a different diameter?

I might also replace the fuel pump feed hose, at the tank... that's the original, and my car's got 238,000 miles on it. I can't quite figure out (by looking) how it attaches to the tank, though... looks like some strange compression fitting? Either of you guys replace that?

 

Strange; I figured I'd have a ton of responses to this question from the TPI members. Did I ask a difficult question? Or am I confusing some of you because I have a V6? The V6 MPFI uses almost the same exact system, guys... and to think that only two guys know what happens with a higher flow fuel pump and stock injector is a little strange.

 

They are shunning you.

Sure, you can measure the outside and get close. Keep in mind the ID is what you need, but the tubing is fairly thin wall so just subtract a little, and thats the size. It might be a total of 1/16" you need to subtract. It would be everything that needs replacing if its too small, not just the rubber pieces. I'm not sure how 1/4" line would fare but I'd be surprised if it was that small.

The line at the tank isnt a compression fitting, its a flare nut of sorts. Just unscrew the nut from the fitting on the rubber hose, and it will come apart. I've never replaced one, they seem to hold up pretty well.

 

Now that I'm thinking about it, something is telling me you won't have to worry about it. I could be wrong but if I remember correctly the fuel pump used in the V6 fiero is the same in the V8 F-body.

I just checked the HoLLEY website and thier high flow 255 pump is par number 12-903. It's listed for both the 5.0/5.7 f-body and the 2.8 Fiero. You have the MPFI V6 don't you. Either way, you shouldn't have to change anything, unless of course your not running FI to begin with.

Am I confusing you yet?

Eric.

 

CraZ, nope, not confused yet! Thanks for doing that part # search, didn't even think of checking out high flow V8 pumps! Yeah, my motor and the Fiero motor are almost identical, except the Fiero motor is tranverse mounted, has better factory exhaust manifolds, and had a larger throttle body (made by Holley).

Madmax, they probably are- its happened many times before! Oh well. Glad you guys are responding! I'll try to measure that line this weekend.. ugh, I hope it's not 1/4". There's not many -- okay, there aren't any -- TPI V8 motors in the junkyard around here. That'd be a hell of a line to pull. I had to swap a front-to-rear brake line to get my 3.73/posi/disc axle (from an '84 t/a) to line up at the prop valve, that was bad enough.

You sure there's a flare nut up there? I saw a flare nut on one side of the hose, but not the other- it looked like the hose was somehow crimped to the tank outlet. GM told me they wanted $40 for the hose, but it was a special order, about 2 weeks- and both times the fuel pump died, I wasn't prepared for it. This time would be great to change that poor hose. Last time I changed the pump, it was looking worn out, lots of cracks, and the flare fitting was pretty rusty.

 

O I C

The end on the tank side might very well be crimped onto the line. I dont remember to be honest with ya. If all else fails though, you more than likely could just use a rubber FI line, bubble the ends of the lines you cut off (the tank side is probably barbed though) and clamp it in place with regular hose clamps.

 

not much hell there are 8 22 lbs injectors if a prob get some of a lt1 25 lbs