Delphi Mechanical Fuel Pump stops pumping fuel

[siteunseen]

I remember Fastwoman bought a fuel one way check valve from "sam the diesel man" on ebay. Many years ago but you might find him still. Good luck.

[HappyZ]

I tried to read everything you've done and what others have posted, so forgive me if you've already done this.  Have you fed the intake from the fuel pump directly into a bottle of fuel to test from the fuel pump to the carbs.  When I replaced my pump, I had similar problems.  I ran one 16oz water bottle filled with fuel and everything cleared up.

Edited May 2, 2020 by wadelester

[w3wilkes]

Going electric really isn't a big deal. The 240Z's come wired for an electric pump. It's a matter of putting in the jumper at the front of the console area to power the already existing circuit and adding an inertia switch in your jumper loop to kill the pump in the event of an accident.

[David Downs]

5 hours ago, w3wilkes said:

Going electric really isn't a big deal. The 240Z's come wired for an electric pump. It's a matter of putting in the jumper at the front of the console area to power the already existing circuit and adding an inertia switch in your jumper loop to kill the pump in the event of an accident.

I noticed online a factory electric pump upgrade kit to install the pump. It included the small wire harness you mention, pump and bracket, 2 relays, and harness A&B. I would prefer to use as much factory wiring and install the inertia switch near the console. Can you recommend a parts list?

 

[David Downs]

21 hours ago, wadelester said:

I tried to read everything you've done and what others have posted, so forgive me if you've already done this.  Have you fed the intake from the fuel pump directly into a bottle of fuel to test from the fuel pump to the carbs.  When I replaced my pump, I had similar problems.  I ran one 16oz water bottle filled with fuel and everything cleared up.

Yes, I have tested the pump function. I really think installing an eccentric that has more lift would increase the pumping function. Does anyone make an eccentric with more lift? 

[w3wilkes]

My electric pump install is on like the 3rd page in this thread;

There's a ton of good info all through the above referenced thread. The wiring for electric fuel pump was included in the factory harness. There's no need to add additional wiring other than the short jumper loop at the console to power up the existing harness. It turns the pump on when the car is in the run/start positions only. There's no relays to add, just a method for fuel cutoff incase of an accident.

And here's a link to the cutoff switch you can put in the jumper loop.

https://www.amazon.com/Ford-5L2Z-9341-5L2z9341a-Inertia-Safety/dp/B000NTI03C

Edited May 3, 2020 by w3wilkes

[cgsheen1]

21 hours ago, David Downs said:

Yes, I have tested the pump function. I really think installing an eccentric that has more lift would increase the pumping function. Does anyone make an eccentric with more lift? 

Have you given thought to installing the mechanical pump without the spacer - just to see if that makes a difference?

[David Downs]

15 hours ago, cgsheen1 said:

Have you given thought to installing the mechanical pump without the spacer - just to see if that makes a difference?

Yes I tried installing the pump without the spacer. The pressure between the pump arm and eccentric was really tight. 

[cgsheen1]

So you couldn't complete the installation? (to see if it would consistently pump without the spacer) I wonder if anyone has been able to compare the arm geometry between the original fuel pump and these aftermarket pumps. If the arm geometry is the same then GMB and Delphi must be doing something different inside the pump.

Sadly, I guess I'll be playing with this myself. I have a customer bringing in a 72 with similar symptoms. Been pulling his hair out swapping mechanical pumps. He wants me to install an electric fuel pump. I'm an EFI guy - abandoned carbs in the '80's and have avoided them as much as possible since then. While I have the '72 I may look into this mechanical fuel pump issue. I think all the eccentrics are exactly the same but I have a couple of them to compare. Wish I had a Nikki pump...

[tetert1]

And My 72 Z was doing the same thing I did about all the same things you did. I bought clear  hoses from Amazon 5/16 and quarter inch and fuel pressure gauge and install them so I could see what the fuel was doing to carbs. If you don’t have clear fuel hoses you’re blind unless you have x-ray vision .I was getting air bubbles to theMechanical fuel pump low Pressure and carburetor float bowl’s making the engine run lean and run hot Hot exhaust manifold  and muffler.Vapor lock in fuel line I check my timing on my distributor it was set to retard.  I advance the timing to 5°or 10• BTDC  now the engine runs a lot cooler and no more air bubbles vapor lock So maybe your engine is running too hot and lean because your exhaust manifold is right under your carburetor float bowls Also check your  Guide  flow valve next to your coil. three-way valve ,blow it out see if you can hear airAnyway that’s what happened to my Z hope this helps..Also it helps to have a half to 3/4 gas in your tank

Edited May 4, 2020 by tetert1

[David Downs]

On 5/4/2020 at 10:53 AM, cgsheen1 said:

So you couldn't complete the installation? (to see if it would consistently pump without the spacer) I wonder if anyone has been able to compare the arm geometry between the original fuel pump and these aftermarket pumps. If the arm geometry is the same then GMB and Delphi must be doing something different inside the pump.

Sadly, I guess I'll be playing with this myself. I have a customer bringing in a 72 with similar symptoms. Been pulling his hair out swapping mechanical pumps. He wants me to install an electric fuel pump. I'm an EFI guy - abandoned carbs in the '80's and have avoided them as much as possible since then. While I have the '72 I may look into this mechanical fuel pump issue. I think all the eccentrics are exactly the same but I have a couple of them to compare. Wish I had a Nikki pump...

When I purchased the car I replaced the fuel pump without the spacer. I didn't realize the spacer was still attached to the original pump that was covered in grease. The car ran fine for about a month. I thought the pump was damaged from leaving off the spacer. Ordered another Delphi pump with spacer and installed it. Drove it around the neighborhood for an hour until she left me stranded. Towed her home, ordered the GMB pump, and got her running again. I will give her a long test drive after the fuel check valve is installed between the filter and carb. In my opinion, the pump lever needs more lift. It's like pumping up a bike tire and not giving it a full up and down motion. Wish I had a Nikki pump as well so I can compare them.

[Zed Head]

You might try some experiments, moving the lever by hand, to see when in the stroke the pump actually moves fuel.  There might be too much play at the beginning of the stroke.  Could also be that the leaky valves inside allow too much fuel past on each stroke.  

If the problem is play, you could stack some gaskets to create a thinner spacer, to take up the play.