Fuel Pump Help

R

rhoadesm

True Classic
So I replaced my fuel pump with one from Midwest Bayless. There were no instructions in the box so I assume the hoses fit on the new pump just like the old pump, from tank to nipple closest to engine and to carb on the nibble closest to the firewall. It appears that it is not working as my fuel filter is not filling up with gas, my filter is on the hose after the pump. So what could be wrong? And before you ask, yes I did put the pump push rod back in.

Also just so others know, the gaskets that came with the pump did not match the originals and would be blocking the holes for the oil (I assume that is what the holes are for). I made my own for the on between the spacer and the block and I modified one of the ones that the pump came with. Even the gaskets that Midwest shows on their site did not match.

Here is the pump on their site, pump, it looks a bit different in that the nipples are closer together and they are the same height, maybe it is just how they look in the picture.
 
There is a procedure on page 58 of the manual (downloadable from Wiki) for setting the stroke for the pump. I'm not sure that would keep it from pumping but I think it can cause damage if it is too far off.
 
A lot of pump have arrows stamped somewhere on them to show inlet and outlet. I'll give the same advice I always give, check with MWB, their customer support is amazing.
 
This is the pump from a 124 sedan, but yes, if you don't get the spacing right on the pump shaft you can fracture the pump housing. Been there, done that, switched to an electric pump. :)

Look at the "new" pump on the right. Lost an ear, fractures in the body. Poor little guy only lasted a few weeks. :( It was my first attempt at replacing a mechanical pump, I put a second one on and did a better job of spacing it. However, in the end, I decided to go electric.
broken fuel pump 4.JPG
 
When the 74' arrived, it had the OEM mechanical fuel pump. Worked good, unless the exxe was not driven for a while. This allowed the fuel in the carb's fuel bowl to evaporate. It took LOTs of cranking to get the mechanical fuel pump to prime then fill the carb.. Not tolerable. Think within the first week of the 74's arrival, the OEM mechanical fuel pump got extracted and replaced with a Facet cylindrical ticker, inertia off switch and pressure regulator. Since then, the routine to star up the 74', power up the system to get the fuel pump running and fill up the carb, pull up on the choke cable, turn the key to run the starter.. 98% of the time the Lampredi engine starts up first crank..

The stock mechanical fuel pump needs to be shimmed using the gaskets supplied to achieve proper fuel pressure. This means setting up a fuel pressure gauge at the fuel pump's outlet and experimenting with the gaskets to get the proper fuel pressure. This also means on-off with the fuel pump more than a few times.. Not fun at all. Other possible problem, the mechanical fuel pump might have problems priming or pulling fuel out of the tank to begin the pumping process. While you're at this, replace all related fuel hoses as they are more than likely tired and needs to be put to a place where they can rest... for good.


Check these.
Bernice
 
It's odd, I have been playing with Fiats on and off since 1967 and I never knew before this thread that you have to shim the damn fuel pump. Why would Fiat even provide pumps that require this. Valve shims I understand but Fuel pump shimming! Good thing I automatically put electric pumps on all my Fiats for the last thirty years.
 
The stock fuel pump needs to be shimmed to obtain the correct clearance, its not a difficult procedure. I agree though electric fuel pump is the way to go

 
How are you supposed to measure that distance with the pump being where it is. I came up from below and was not too big of a deal, just had to remove the oil filter which was OK as I had to change the oil anyway.

Since I had to make one of the gaskets I am thinking the material I used may have been too thick as the gaskets that came with the pump were pretty thin. Maybe I'll just write off the new pump and go electric, I guess I better start researching how to do it.
 
carl said:
It's odd, I have been playing with Fiats on and off since 1967 and I never knew before this thread that you have to shim the damn fuel pump. Why would Fiat even provide pumps that require this. Valve shims I understand but Fuel pump shimming! Good thing I automatically put electric pumps on all my Fiats for the last thirty years.
Click to expand...

Not one for reading manuals I take it? It’s even in the Haynes manual

:)
 
Off on a bit of a tangent here. I want to instal and electric fuel pump just to act as a primer. As has been mentioned before, after a spell of sitting idle there is a fair amount of cranking before it fires-off. This is hard on the starter, the wiring and the battery. Would installing the pump right into the fuel line before the mechanical pump or have a bypass around the mechanical pump?.
 
K, I think it never occurred to me that adjustment was required. I pretty much went exclusively to e-pumps anyway. Any day I expect to find out the valve cover needs to correctly shimmed.

Peter, if you are going to install an electric pump for starting, why not just use it all the time?
 
carl said:
Any day I expect to find out the valve cover needs to correctly shimmed.
Click to expand...
Wait, you haven't been shimming your valve covers? I'm surprised you haven't had issues due to that, like the car rolling into a light post. :rolleyes:


carl said:
Peter, if you are going to install an electric pump for starting, why not just use it all the time?
Click to expand...
I second that. Frankly I'm not sure a twin pump system would work anyway, at least not without an elaborate system to control the flow from each one.
 
rhoadesm said:
Maybe I'll just write off the new pump and go electric, I guess I better start researching how to do it.
Click to expand...
If you go this route, start by reading the current thread that discusses electric pumps. Or any of the older threads on the topic. There are a LOT of bad ones for sale out there.

Fuel starvation after prolonged high RPM

Hi all, I was driving to work today and (as the autobahn was nearly empty) I accelerated to about 160 km/h (6000 RPM in a 4 speed). The car is a 1300 with a single 36 DCNF. Accelerating is fine, but after running at 6000 RPM for longer than about 30 seconds the car seems to lose power. Slowing...
xwebforums.com
 
rhoadesm said:
How are you supposed to measure that distance with the pump being where it is. I came up from below and was not too big of a deal, just had to remove the oil filter which was OK as I had to change the oil anyway.

Since I had to make one of the gaskets I am thinking the material I used may have been too thick as the gaskets that came with the pump were pretty thin. Maybe I'll just write off the new pump and go electric, I guess I better start researching how to do it.
Click to expand...
There isnt much room between the pump flange and the firewall but you could use a small dowel rod or something similar and just mark or calibrate it, then measure on the bench. I replaced mine recently and went in from the top after removing the hood/bonnet. Have you tried priming the fuel lines with gas to remove air pockets inline to the pump? You might just have a big air pocket in there and cant pull gas
 
After reading all the above fuel pump isssues I am also sold on an electric fuel pump. MWB has a FACET pump that looks great for the money. Have had electric pumps on many previous non-FIAT cars and work a treat on cold sarts on odd-week-ends.
My next question is what to do with old mechanical pump. Leave it in situ with crimped hoses. Remove actuator and put it mechanical pump back. Have a blank made from gasket/spacer as template ?
Also where to locate fuel pump and what wire to run to it from where in the engine wiring ?
 
carl, Dr.Jeff..thanks for your input. The mechanical pump works fine at the moment once fuel lines and carburetors are charged. I am hoping to avoid the requirement of prolonged cranking after extended lay-over. The upside is that the oil pressure is up by the time the engine lights-off. I was envisioning a couple of T pieces off the fuel line to feed the electric pump before the mechanical pump. The idea is to prime the system.
 
A mechanical pump can be as or more reliable than an electric. My carbed cars have had their mechanical pumps from new. 50 years of reliable service is pretty good...at least in my mind.

This rush to add another semi reliable complex sub system to the car is a choice but one I wouldn’t make without also adding the needed safety system to ensure it shuts off when the engine stops running and the inertia switch which a few have added.
 
It’s interesting my old 1500 always took 10s or more of cranking before it would fire if the car had been laid up for a while. My 1300, touch wood, fires up within a few seconds, both had the original mechanical Pump
 
Consider why the vast.. vast majority of modern cars today have electric fuel pumps with an excellent record of reliability, durability and service life.

There is a mechanical fuel pump in the TR3, it has been in service for a LOT of years and continues to function well to this day.

Both fuel pump designs can get the job done, as with any design trade-offs are enforced and required and choices will be made based in a very long list of considerations.


Bernice
 
Starting from a three year lay-up with cleaned tank, strainers, empty metal filters and lines to new mechanical fuel pump and empty carburetor bowl. How much cranking before it starts. Particularly with only static timing of new distributor. Was thinking aerosol ether down the carburettor throats with lid on filter in case it 'burps' A temporary FACET electric to prime system then remove it once fuel system is fully primed and engine running.

Michael
 
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