# Mechanical fuel pump update



## chickenfriend (Jan 31, 2005)

*Mechanical fuel pump update Airtex 60238*

I just inspected then replaced the Carter M 60238 mechanical fuel pump on my 1.7L Rabbit. The pump was purchased from Autozone in 2005 so it is 7 years old. 

This pump was designed to be used on the Dodge Omni and Plymouth Horizon 1.7L carburetor autos, but works on some VW engines due to the same block design and intermediate shaft.

I had some driveability problems in the summer with the fuel system, found some problems and made some changes, but I did not inspect the fuel pump.

Having just removed the radiator for replacement, I thought it would be a good time to check it. Since it seemed to have had some leakage out the weep hole, I destructively disassembled it. The diaphragm was in good shape, generally, although some deterioration cracking had started on the membrane. There was a dark stain under the lower diaphragm pump chamber weep hole. There was some very slight play between the holding rivet and the holding plate for the top of the diaphragm. This may have been leaking a very small amount of gas into the dry chamber, but it was impossible to tell without pressurized testing.

The two check valves seemed to work in the proper logical manner from me blowing or drawing on the chambers, although compared to a new pump, the resistance to air was much much less.

Autozone no longer carries this pump, which was a Carter pump manufactured in Canada. At one time, this was distributed by Airtex, because I saw their sticker on the box.

Now, Autozone carries Airtex's own mechanical pump 60238, assembled in the USA, which is nearly identical to the Carter in outwardly appearance. 

The pump I bought had the two paper gaskets necessary, but lacked the thick plastic spacer. The Airtex catalog shows the pump with the spacer.

Airtex tells me that their check valve rubber membrane has been upgraded to an elastomer that resists degradation from gasohol. The pump diaphragm used is a resistant polymer, as well, they claim.

I was alarmed when I first saw the Airtex pump because it appeared to lack a restrictor in the fuel pump return port. This restricts the flow of gas to a hole between 2 and 3/64".

However, looking into the pump chamber with a penlight, I was able to see that indeed the Airtex had a restrictor, hidden inside.

Both intake and output ports are 5/16" hose barb, and the fuel tank return is a restricted port in a 1/4" hose barb.

Airtex says to prelube the arm and pivot points with grease before installing. The pump comes with two paper gaskets, but does not include the necessary 1/2" insulator that goes in the middle of the gaskets. You can reuse you old insulator.

Inside each pump chamber of the old Carter pump was a coarse screen. I presume the Airtex has them as well; it is a precaution to keep debris from getting in the check valves.
Airtex states that this pump is assembled in the United States.


All and all, the Airtex seems like a very good choice since you know the rubber parts are alcohol-resistant to deal with our 10 percent gasohol.

I run my fuel lines around the alternator, and has some insulation on them where they pass underneath the top radiator hose.

Other Applications
DODGE OMNI 83-79 L4-1.7L Mechanical Fuel Pump - 
PLYMOUTH HORIZON 83-79 L4-1.7L Mechanical Fuel Pump - 
PLYMOUTH Turismo; 105 (1.7L) 1983 Mechanical Fuel Pump









Maximum Free Flow Rate (gph): 30 
Maximum Pressure Range (psi): 6 
Minimum Free Flow Rate (gph): 30 
Minimum Pressure Range (psi): 4.5 



It is important to note that this pump is not listed for VW applications, so you have to drill for it under the Chrysler applications noted above.

Incidentally, for VW carburetor applications, Airtex sells an electric pump for use with an oil pressure switch that keeps the pump off if the engine is not running. This is a safety feature. The fuel injection pumps have this safety mechanism too, but it is done by a tachometric relay, instead of an oil pressure switch.

This is Airtex pump E8016S UPC 080044089940 Type Solenoid Volts 12 
Inlet/Outlet Size 5/16 hose 
Pressure 2.5-4.5 PSI 
Flow (GPH) 30 

Note the pressure output of the electric pump is the ideal range for use with Weber carburetors, so a pressure regulator is not necessary.

I''ll stick to the mechanical pump for now, but there are advantages of having an electric pump, namely, much less fuel hose in the engine bay (good hose is 6$ per foot and I bet there is at least 10 feet), less chance of vapor lock, less clutter.

I should mention that my carburetor is Weber DFEV with the Cannon manifold.


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## mouser98 (Apr 30, 2012)

great write up on that fuel pump :thumbup:

alas, i had to go back to an electric pump after having chronic vapor lock problems with the mechanical pump.


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## chickenfriend (Jan 31, 2005)

Thanks.

My new mech pump is working fine. I still get a little heat soak problem or something on a warm re-start, say 10-15 minutes after off, adds about double the cranking time compared to a cold start.

I insulated my fuel lines pretty well, so I am not quite sure the reason for it. Check valve on the pump should keep the fuel from flowing backward to the tank.

Might be something about my carb, slight leak of the needle valve or something. Didn't used to do that.

Other options considering are adding a stainless heat shield over the exhaust manifold, cut out around the carb. Would use the existing studs on the manifold as mountings. I have the mk3 manifold.

Another option would be to wire a mk2 underhood temp switch into my radiator fan switch to keep the fan for a while after shut-down.


The electric pump makes a lot of sense however, if it is wired-up safely. I would think the immediate pressurization of the fuel lines would help reduce hot-soak start problems, aside from the other benefits mentioned. It would pay for itself just in cost savings by elimination of extra fuel hose, priced about 6$ per foot here for quality hose.


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## chickenfriend (Jan 31, 2005)

Just a little update on what I just posted above, regarding the extra cranking for hot starts.

One thing that is conspicous after shutting off the engine is a gurgling sound from the carburetor, a Weber DFEV 32/36 with the Cannon/Redline intake manifold. This sits directly over the exhaust manifold, in the mk1 stock counterflow configuration.

I figured this was either air or vapor getting forced into the gas bowl or gas boiling. 

I disconnected the fuel input hose after the engine cooled down some but while the carb was still making boiling noise. There was no pressure in the line, and that made no difference to the gurgling frequency.

With the air cleaner off, I looked down into the carb. The fuel bowl is open to the atmosphere and the fuel in the bowl can be seen by looking into a narrow opening next to throttle bores, with a pen light.

I could see the fuel bubbling, or boiling. This goes on for quite a while. After about 15 minutes, I looked at the level and it appeared to have dropped, although I didn't measure it.

My guess is that because of the heat soak from the exhaust manfold, the fuel is boiling and evaporating out the carb. This may account for the fuel smell I occasionally notice outside my car. 

I am going to have to examine this problem closer, and do some testing, watching the level of fuel over time in the bowl.

10 percent alchohol in the fuel is going to lower the boiling point, so I expect this perhaps why I never had this situation years ago.

If a lower fuel level in the carb bowl causes a hot start problem, then I wonder why the lower level would not cause a problem in a cold start? Perhaps that could be because in a cold start, the choke is activated making a richer mixture?

I am going to experiment with adding a heat shield over the exhaust manifold to see if that helps.

At some point, I may wire in a mk2 engine bay temp switch to the radiator fan, or put an aux manual override switch on the dash, in order to remove some heat after shutting the car down. I like this idea in preference to a heat shield, since heat in the intake manifold is good while the engine is running, in order to better vaporize the fuel in transit between the carb and the combustion chamber.

At any rate, there is lots to play with here. For the time being, I have stuffed some aluminum foil between the exhaust manifold and the intake manifold.

Update: still having this problem with fuel boiling. At least now I know the technical name for the problem, and that is "fuel percolation".

I think there is a lot of heat coming through the carb base. I will move from my 1/4" insulator spacer base to something thicker, and put plastic washers under my stud nuts.

It is very annoying and gas is running out along the throttle plate shafts.


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