Pinto fuel pump

[John Green]

I have installed a new mechanical pump on the Pinto and not getting any pumping action. The plunger is 2" long and there is a 1/4 spacer. I have been suspicious of a weak fuel delivery with the old pump, thus the new one. I understand there are two different length plungers as well as different thickness spacers. Anyone know the correct dimensions or should I just eliminate the 1/4" spacer and see what happens?
Thanks!

[Lotus7]

I don't know the answer, but I'd wait for one, rather than bolting together something unknown and risking needless damage.

[tlracer]

The 2-litre plunger is 50mm long and around 9mm dia. There's a shorter plunger, but that is pre-82 1.6 litre Pinto only. The spacer is intended to be there - mainly as a heat insulator between the block and pump. Don't remove it or you risk shattering the pump.

[Rick Kirchner]

you could make an aluminum plate with a hole to accommodate the pushrod, then remove the plugs and spin the engine to see hos much action you are getting, and then compare that to the pump.

[JHerscher]

I truly am hoping to help and not insult your intelligence, and I hate to ask these questions and I'm sure you have checked but...

1- Does the new pump work? Do you get suction on one of the pipes when you bench test?
2- Is it installed correctly? Some of the correctly numbered AC pumps have the fittings clocked weirdly for our mid-engined applications and beg to be installed upside down. I always confuse myself and mark the fittings to avoid this.

Is this a FoMoCo or AC pump? or an aftermarket pump? In addition to those pumps, I have found the Carter pump works well and will deliver fuel properly. It is around $55 vs over $150. There are several aftermarket pumps that work well for the street version of our engines, but not for race. I have experienced at least one that was problematic.

Others may have different opinions, including the advice to switch to an electric pump. In over 20 years racing these engines, I've never concluded that was necessary with a quality mechanical pump.

[John Green]

I measured the push rod at 2" - 50.8 mm. So the length seems ok.
The spacer is 1/4" same as I have always had on these engines. Fuel is getting to the inlet side. The pump is the one from Pegasus that can have the push on fittings that can be moved. I removed the pump and rotated the engine and the pushrod moves.
How do I bench test one of these?

[John Green]

Hmmm, the pump has an arrow point up at one of the fittings, I assume that indicates the inlet side???

[Steve Davis]

Hard to tell without a picture.. but if the 'pointy end' of the arrow is pointed AWAY from the fitting, that would be the fuel OUTLET! If pointing TO the fitting, it's the INLET.
Steve, FV80

[JHerscher]

If there isn’t an arrow indicating flow direction you can check this way. Hold the pump in your hand, plunger on the work surface, finger over one of the fittings. Push down , relax, repeat. You are cycling the pump plunger through its motion. You should feel suction under your finger on the input side. No suction, switch to the other fitting. The spring should be pretty stout, so expect to push hard. You’ll get about 1/2” stroke. If no suction on either end, you might have a dud.

[Purple Frog]

Memory is getting rusty. But on some odd chassis configurations we ran the pump without the spacer and a shortened rod. So, if you use the spacer and a short rod, then the pump won't work. But, you knew that already.

[JHerscher]

Could the poor delivery of the old pump be related to a clogged fuel cell vent line? Either the line physically blocked by something or a stuck one-way valve?

This would show up after some time as the fuel was consumed and a vacuum built in the tank making it more difficult for the pump to overcome.

[kea]

Memory is getting rusty. But on some odd chassis configurations we ran the pump without the spacer and a shortened rod. So, if you use the spacer and a short rod, then the pump won't work. But, you knew that already.

Froggy,
We removed the insulator spacer and shortened the push-rod accordingly on the 87 and up Reynards, to gain clearance to the frame when the limited supply of short height 2Ltr. fuel pumps dried up.
Otherwise, I would recommend keeping the standard arrangement.

[azjc]

'87 Reynard - using short rod & no spacer as Keith noted. Check the travel of the rod, measure how far it extends at max travel, check the depth of the plunger & make sure the rod contacts & pushes on the plunger. If it does then bad pump? if no contact then wrong rod?

[John Green]

Latest....
I have tried 3 pumps. Two were spares with some use and one brand new one.
All three have fuel to the inlet but it goes no further. I have started the engine by adding fuel to the float bowl, but no fuel gets delivered and the engine quits. Using the in spec push rod with 1/4 spacer. Same set up for years.
I measured the travel of the push rod at 6.8 MM of travel.
I will check the vent tube for any blockage, however the fuel is at the inlet fitting.
I thought maybe the cam lobe for the pushrod is worn effectively shortening the stroke. I don't know if 6.8 mm is in spec.

[DaveW]

There have been cases of fuel suction lines deteriorating internally and peeling off the inner layer. This creates a flap which closes off the hose as soon as significant fuel starts to flow.

Your symptoms sound to me like a blockage between the tank and the pump inlet.

[John Green]

Thanks Dave, the car has all new fuel lines and when I disconnect the line from the fuel cell and hold it below the level of the cell outlet, fuel flows out easily.

[hdsporty1988]

Thanks Dave, the car has all new fuel lines and when I disconnect the line from the fuel cell and hold it below the level of the cell outlet, fuel flows out easily.

John, with the condition Dave was referring to, fluid could flow during your test, but the line collapse under suction from the fuel pump. Do you have a vacuum pump that you could put on the line to create suction? Bruce

[John Green]

John, with the condition Dave was referring to, fluid could flow during your test, but the line collapse under suction from the fuel pump. Do you have a vacuum pump that you could put on the line to create suction? Bruce

Thanks Bruce, I'll check that.

[tlracer]

Latest....
I have tried 3 pumps. Two were spares with some use and one brand new one.
All three have fuel to the inlet but it goes no further. I have started the engine by adding fuel to the float bowl, but no fuel gets delivered and the engine quits. Using the in spec push rod with 1/4 spacer. Same set up for years.
I measured the travel of the push rod at 6.8 MM of travel.
I will check the vent tube for any blockage, however the fuel is at the inlet fitting.
I thought maybe the cam lobe for the pushrod is worn effectively shortening the stroke. I don't know if 6.8 mm is in spec.

I had a new pump go bad in exactly the same way, no fuel flow out to the carb. I didn't believe it had failed so soon, but proved it by taking it off the engine, blocking the inlet and outlet with finger and thumb, then operating it by pumping the actuator rod on my workbench. Not technical, I know, but it showed I had no suction, ie. the pump wasn't sealing internally.

[John Green]

I measured the stroke of the pushrod relative to the movement required to cycle the pump diaphragm. I installed a just slightly thicker spacer to allow for full movement. That got the pump working only to see that the newly installed fuel filter was not filling (installed after the fuel pump) I suspected there was not enough vacuum to get past the filter. Took it out and everything works just fine.
Thanks for everyone's input.