cdrad51

Did a search and found several people have fried their fuel pumps, but couldn't find anybody who had found a definitive cause and remedy. Here's the data on my case:

I'm having problems with my Carter fuel pump (purchased about 3-4 months ago). However I have not fried it yet. What has happenned, is that after driving for more than half an hour, the fuel pump seems to stop flowing gas, even though it can be heard running (if I'm at idle otherwise the engine drowns it ). It has happenned twice now, both on highway driving. The first time I was almost at my destination when I noticed depressing the accel didn't do anything. I was out of fuel. I took the next exit and found a spot to park. Opened the hood, put the ign switch in the on position, and the fuel pump was making a whirring sound, but not the usual one. My FPR's guage was showing 0 pressure. Fuel level windows showed no gas in carb bowls. Touched the fuel pump, it felt hot. After waiting for about 1/2 and trying again, it went back to normal. Pressure, fuel at the appropriate level. Drove back home for about 40-50 mins with no problem, although I was driving very conservatively, 60 mph on the right lane of the freeway. That happenned about a month ago. Then today I had to do another freeway trip. Noted nothing. 20 mins after arriving at my destination, I took off to come back. Got on the freeway ramp, floored in 1st, redline, floored in 2nd, redline, floored in 3rd, car bogged down from lack of fuel. Damn! Had to drive for 40 mins at 60-65 mph. Arrived back at the office, opened the hood, put the ign key in the on position, no pressure and the fuel pump is doing a different whirring than the usual.

So it would seem that the pump is running hot, causing it to fail at some point. Now I have to figure out why. One thing I know is that the fuel pump is supposed to be vertical for optimal cooling of the motor, and is in fact in an slight angle. Well, maybe not slight. Here's pics of how it's placed, though the angle is not easily discerned from the pics:






As you can see in the pics, the fuel pump is relatively close to the rear axle. When I touched the rear axle/differential after coming back to the office, I noticed it was hot too, maybe due to old LSD (it whines a lot) which probably radiates some heat and doesn't help cooling down the pump particularly. My fuel tank is the original one AFAIK, but doesn't seem to be in too bad a shape, judging from how long the fuel filters last. However I wouldn't discard the possibility of partial clog being part of the problem.

Any suggesstions? similar experience?

trochoid

iTrader: (6)

My Carter did the same thing last week. Towed it home, pushed it into the shop, damn thing started right up. When it quit it was dead silent. No noise or pumping at all.

Your pump sounds like it is vapor locking. The pump gets hot, the fuel goes to vapor and cannot pump air.

Did you bypass the stock fuel lines and run hose all the way to the engine bay? I can't tell for sure by your pic. If that is the case, your pump may be working harder that it needs to.

BTW fix those oil leaks and degrease. A clean car is a happy car. And an even happier mechanic.

cdrad51

No, I'm using stock lines. The only thing I did is eliminate the cut off valve or whatever is called, the one that would be on the rail to the left of where the pump is in the pics.

I just went out and tried it again, 2 hours after I came back. Pressure OK, fuel pump operating fine. So it's definitely temperature related.

Vapor locking, sounds about right. But why??

RotorMotorDriver

iTrader: (1)

I had my Carter pump mounted in the same spot on my RX-7 and NEVER had a problem with it. Although, odly enough I now have it mounted vertical on my Toyota 4x4, and it did what you are describing. HOWEVER, I installed it on my truck because the aftermarket fuel pump that was on it for the Weber was dying, or so I thought. I had the EXACT same symptoms you described with my fuel pump BEFORE I even put the Carter on. I put the Carter on hoping it would stop the problems thinking the pump on there was going out, but it still does it. Now Im not sure if its the tank in the truck getting the pickup clogged by something (rust flakes and crap?), or the pump as this is the first time Ive ever heard of anyone having a problem with their Carter! I did notice however, that while my pump is still whirring and not pumping, I can take the hose off the output line and suck through the pump as it pumps and get it going again right away, its like it looses it vacuum for whatever reason and cant self-prime or something. Its weird because it just takes a little vacuum on the line to get it going again, its not like Im sucking fuel all the way to the pump. I dont know, its baffling!

~T.J.

cdrad51

Yeah, I'm thinking maybe it's a combination of the two. Like a partial clog caused by rust/sediments causes the pump to work harder to keep the flow going, which raises its temperature, eventually getting to the point where there's vapor lock, and then no chance of cooling down using gas, fuel pump fails. I guess theoretically if one keeps going, it will totally fry eventually. I'm gonna take a closer look this weekend and see what I can find along this line.

d0 Luck

i thought u bought a purolator fuel pump cdrad?

Rx7carl

I had a mfg defect cause a failure. But that was an internal short in the windings that would pop the fuse on it. Replaced the pump under warranty and no trouble since. I have mine mounted in the same place as yours Carlos so I dunno. Maybe it is sediment in the sock.

cdrad51

That was last year.

mar3

iTrader: (8)

You're making the pump work too hard...is this photo still correct?



You can clearly see the pinch...even a superior Mallory would have a hard time with both lines getting constricted like that...

mar3

iTrader: (8)

Oh, the beloved Mallory's...

cdrad51

I knew you'd come sooner or later

The photo is when first installed. I spotted and handled that pinch shortly after.

CarlRx7

one problem i see is that the fuel is traveling down to the fuel filter then BACK UP to the pump.

if the pump cannot get a good syphon going its gonna burn up the pump or vapor lock like describe above.

you need to mount the fuel filter higher. above the pump. cut the metal line thats coming down. and mount the filter up there, then run a line to the pump and let us know if that helped.

carl.

Rx7carl

Carl may be right, that could be the problem. Your gettin slow in your old age Mario.

diabolical1

iTrader: (3)

Hey Mar3 ~

do those Mallory pumps have to be mounted upright like the Carter? if they go horizontal, then you'll probably have a new evil disciple as soon as it's convenient for me to get one.

Pele

iTrader: (28)

Won't problems in the vent and evaporative system also cause vapor lock?

What happens if you leave the pump whirring and open the gas cap?

mar3

iTrader: (8)

Yea, what happens? The Mallory is supposed to be up and down also....however there's plenty of room and I'll draw what I'm talking about since I haven't actually installed my Mallory yet.......d.....oh......

cdrad51

Good point. I'm going under the car today and will re-arrange things for better flow. Will let you guys know how it went.

Brianhsval

As for what I know about vapor lock, re-arranging things will not help. But then again what do I know. Vapor lock occurs when gas boils, due to high temp as well as high altitude. What am I missing here? I would think that venting, which has already been mentioned, would be the way to go.

numan2

I'm using a holley red pump mounted horizontal right where the wires feed through the grommet on the botom of the floor pan and never have these kinda problems

IanS

iTrader: (4)

You mounted it horizontal? The instructions say that it has to be vertical (with the in and out on bottom).

mar3

iTrader: (8)

And yet, he has never had any problems!!....Things that make you go , "Hmmmmmmmmm...."...

numan2

maybe I'll take a picture later this week when I got th car up on the lift @ work but yes it's horizontal

cdrad51

Well, relocated the fuel filter so it's a bit higher, but still couldn't get it to the level of the fuel pump. Couldn't find a way of doing that. But I'll give it a test to see if the condition improved.

Banana boy, where do you have your fuel filter? any pics?

REVHED

Why not just mount it on the frame rail? It's more solid, quieter, the pump will be vertical and it makes the fuel line routing easier.

mar3

iTrader: (8)

Exactly.......