On the side of the road- fuel pressure: Mass-Flo Fuel Pump Fuse size??

[David Hodgkins]

Took the cover for a small errand today and all of a sudden I lost fuel pressure to about 20 pounds from 40. Started sputtering and I was able to turn around but the car would not accelerate and when I came to a stoplight it died. I’m waiting for a tow truck now. What do you guys think? Seems to me that I lost my fuel pump but why would it still pump at 20 pounds pressure?

any and all ideas or input welcomed.

[Papa]

Debris clogging a line or filter?

[Jeff Kleiner]

Two other possibilities:

1) Fuel filter. The fuel starvation would most likely show up under load and not at idle.
2) Ruptured "S" hose that connects the pump to the pickup tube.

#2 requires pulling the pickup from the tank which may mean dropping the tank, #1 does not.

Jeff

[sread]

If you are running an in tank pump, it is most likely the short hose which connects the pump to the hanger has split or ruptured. You should be able to hear the pump if it is running.

[David Hodgkins]

I have an access hole for the pump cut into my trunk floor so I won’t have to drop the tank (I hope) .

I hope it is the filter because if I blew a fuse from the pos Massflo power module I think I might lose it.

I’ll pull the pump and see if I have a split pickup hose.

Thanks for the fast response guys!

[B Campbell]

Bummer. hope its something simple.

[rich grsc]

Not a filter, that would be a gradual pressure drop, not sudden. Most likely is the short hose on the in-tank pump.

[J R Jones]

David, If that is a regulated 40PSI, perhaps the regulating feature has failed; too much by-pass?
Measure head directly at the pump or defeat the by-pass.
Maybe none of this applies to your EFI.
jim

[David Hodgkins]

So she's back home now. When I have the fuel pump removed I'll update the thread. (With pics this time)

EDIT: The story.
When the car died I was at a light with Newport's finest right behind me. I pulled the flashers before they pulled theirs, got out and pushed the car around the corner so traffic could flow. They followed and stopped behind me when I got the car around the corner. I explained what happened and they offered to call AAA. I said thanks and looked around for a spot to get off the road completely, if possible.

Side Note: As I did this I noticed my plate and it said expired January 2021! ACK!! Luckily I knew I had put the registration in the glove compartment so I said nothing, but got in there and immediately applied the tag I had forgotten to affix! Whew!

I was at the top of hill so it would be easy to coast down the road. I know that on this little stretch - before it goes uphill again - that there is a driveway on the right into a garden center but the driveway was all up hill. Or, I could coast down to the gated community next door and swing into their entrance. So I explained my plan to the officers and they said sure, go for it. I walked over to my car, popped it out of gear, gave a little push and coasted the 100 yards downhill to the entrance and by then I had enough momentum to swing in, coast up the drive and make the u-turn before the gates to park out of the way for anyone coming out of the gates. You just got to love all-manual cars in these situations! The popo let me know they updated the location of the tow for me and off they went. When they left, I realized I needed to call AAA ASAP because I had not asked the officer to specify a flatbed. So I called AAA but as I started to call the tow driver showed up in a standard tow rig. You know, the one that has bars fore and aft of the drive wheels. No bueno! He knew he wasn't going to be able to tow me but he said he had to see the car! So we chatted about it for a few moments and I sent him on his way. Then I called AAA, explained the situation and ordered a flatbed.

Now, some folks think of Newport as pretty hoity-toity. You know what I mean. Snobbish. And here I was, broken down and parked in front of a gated Newport community's private entrance. But no less than 5 people rolled down their window as they entered or exited and made sure I was OK and/or asked about the car. One offered to call AAA. One gave me a cold bottle of water! But the topper was this: I wish I had video of daddy's pretty girl in the white top-down convertible Bentley with her phone out taking pics so you could see her excitement about ol'5269. She was literally yelling "Oh my G__ what a great car!" "What IS it!" "What year is it??" "You BUILT that?!?" Remember, her ride is surely 4-6 times more valuable than mine and she just went gaga over my little MKIII. And for the flat bed driver this was his first cobra. He was talking about how Shelby's Cobra, GT40 and Series 1 are his dream cars. He was super careful, accepted my pointers about hookup and after drop off said I made his week! HE took pictures of course, but declined my offer to sit in it, being in work clothes. I told him about HB, and wouldn't be surprised if he goes. "First weekend in November at the Pier!" is pretty easy to remember I hope...

Moral of the story:

It's hard to have a bad day when you hang out with a rock star.

[Garry Bopp]

Great story, David! It is amazing how much attention these cars get and the way people appreciate them.

Hope the fix is simple!

Garry

[2FAST4U]

Wow! Glad nothing happened and you got the car home

[weendoggy]

#3...if the tank is low on fuel, you'll lose pressure as well.
#4...screen on pump inlet pinched or blocked.
#5...I'm guessing you heard the pump so that would be o.k.

Most important: did you tip the driver? 😎

[David Hodgkins]

/...Most important: did you tip the driver? ��

Always. Even if it is for just a mile like this was. Those guys have a tough job.

[David Hodgkins]

Update and resolution:

I pulled the fuel pump, which showed the hose to be in decent shape. I also Pulled the fuel filter and cleaned it. The fuel filter is a nice piece:


The pump hose has striations on it from wriggling it in and out of the tank over the years but that hose is thick and the striations are surface-level only. Here is a highly-magnified pic showing the condition of the hose. Not pristine, but in working order:


While it was out I put my original 190 lph(?) pump back in, replacing the higher 240 lph pump I put in there as part of a previous diagnostic fail. Seeing the pump in working order meant I had another potential culprit to look at, the dreaded power module for the mass-flo.

Interestingly, the culprit came from that module, but not from the expected source. The 10A fuel pump fuse was intact, but the 25A radiator fuse was blown.

Full disclosure: After being open - with painter's tape covering the opening for a week - there was not enough gas in the tank to get pressure. There was gas in the tank when I pulled the pump, as the filter was wet. I do not think I simply ran out of gas. That being said, I did not add gas and try to start after I broke down.

I added 4 gallons of gas and was able to get ~10 lbs of pressure. The same as when I broke down. But as I cranked the system pressure built and she fired up.

So.

Did I simply run out of gas? I was low, but like I said there was some gas in the tank when I pulled the pump. The lines burped fuel when I took them apart.
If I ran out of gas, would/could it blow to fan fuse???

Well anyway, I'm back on the road. You know, I still love the ol' girl:

[weendoggy]

Question is: is the fan fuse connected to your fuel pump? Is it delivering power to the pump relay or pump itself? Those are things to find out. Could be a coincidence, but I think otherwise. Does your pump have the "pre-screen" on it? Not having enough fuel in the tank will cause loss of pressure and if low and sloshing, will do the same. The 10# is fairly normal on initial fire up of pump and dry tank. I bet if you would've cycled the key a few times pressure would read normal as the system fills with fuel. However, you can forget all of this because you got it running.

[J R Jones]

I worked for a clever fellow with engineering experience in the aircraft industry. None the less, Jerry was down to earth and embraced symplicity.
One cold (WI) winter night, Jerry and Liz were out and about. The family station wagon quit running, much like your replica did. Recognizing it was a fuel flow issue, Jerry ran the tailgate glass down and removed the fuel cap.
Hanging from the roof rack and tail gate, Jerry engaged the filler neck and blew hard enough to push fuel to the carb allowing Liz to start the engine and drive home.
As an OEM chief engineer, I could count on Jerry for guidance, and amusing experiences.
I assume that you did not have an assistant Dave.
jim

[David Hodgkins]

Hey I just noticed that my current power module has a different fuse size than my original power module. For those who know, what size fuse are you using for the fuel pump?

[weendoggy]

Not knowing how yours is wired, I have a 20A fuse controlling my FP relay. That is from the "key on" power, not load to pump, that is controlled by the relay.

[David Hodgkins]

Not knowing how yours is wired, I have a 20A fuse controlling my FP relay. That is from the "key on" power, not load to pump, that is controlled by the relay.

I looks like my original fuse was 20A but when I changed out the box somehow I ended up with a 10A fuse in that position. I don't know how it happened but I'm going to change it back to a 20A.

I read on the net that gas can evaporate quickly. I'm still quazi-sure that I didn't run out of gas. Actually running out of gas would make sense if the fuse hadn't blown.... Wierd.

[weendoggy]

I looks like my original fuse was 20A but when I changed out the box somehow I ended up with a 10A fuse in that position. I don't know how it happened but I'm going to change it back to a 20A.

I read on the net that gas can evaporate quickly. I'm still quazi-sure that I didn't run out of gas. Actually running out of gas would make sense if the fuse hadn't blown.... Wierd.

A lot depends on how the relay is wired to the pump. If it gets its 12v from Key-On to activate, a 10A should be plenty. Once the relay energizes (usually) it pulls straight 12v from Bat + to pump (protected by a suitable size fuse, fuse link or CB). If wired for fuse in-line with the pump itself, I'd definitely put a 20A there. If you use an Inertia Switch, I'd run it for key activation and not load to pump. However, Ford did it both ways. Go figure.

Clarified the 12v from Bat + lead to pump. Some would take this literally.

[J R Jones]

I cannot understand this mix of messages.

The 25A radiator (fan I assume) fuse was blown. That should not be a fuel pump issue. If the fuel pump is on the fan circuit, I would segregate them. They are two high load devices.
The 10A fuel pump fuse was OK. Was that feeding the pump power or the pump relay coil?
I don't know what a power module is.
"previous diagnostic fail" This incident?
A fuse protects the wiring in the event of a device fail or a wiring fail. It is sized appropriately for the wires and the device load.
A 240LPH pump draws more current than a 190LPH pump
The purpose of a relay is to take pump load off a switching device. A pump is high load (big fuse). A relay coil is low load (little fuse)

When a fuel pump is pulled, residual fuel in the lines gravity back-flows to the pump strainer.
When the pump runs dry, air gets into the system with fuel. Pure fuel is not compressible and pressure readings are valid.
Air is compressible and air/fuel pressure readings are not valid.
I would not run power to a fuel pump from the battery. It should be an ignition "on" circuit with an appropriate fuse. Installation data or pump data should list the appropriate fuse size.
jim

[David Hodgkins]

I cannot understand this mix of messages.

The 25A radiator (fan I assume) fuse was blown. That should not be a fuel pump issue. If the fuel pump is on the fan circuit, I would segregate them. They are two high load devices.
The 10A fuel pump fuse was OK. Was that feeding the pump power or the pump relay coil?
I don't know what a power module is.
"previous diagnostic fail" This incident?
A fuse protects the wiring in the event of a device fail or a wiring fail. It is sized appropriately for the wires and the device load.
A 240LPH pump draws more current than a 190LPH pump
The purpose of a relay is to take pump load off a switching device. A pump is high load (big fuse). A relay coil is low load (little fuse)

When a fuel pump is pulled, residual fuel in the lines gravity back-flows to the pump strainer.
When the pump runs dry, air gets into the system with fuel. Pure fuel is not compressible and pressure readings are valid.
Air is compressible and air/fuel pressure readings are not valid.
I would not run power to a fuel pump from the battery. It should be an ignition "on" circuit with an appropriate fuse. Installation data or pump data should list the appropriate fuse size.
jim

Jim,

This is the power module for the mass-flo EFI harness:


It looks new in the pic because I got it at the end of my last bit of roadster drama. It, and the previous failed diagnostic that resulted in a new fuel pump are part of this fiasco:
https://thefactoryfiveforum.com/show...the-road-again!

[i.e.427]

Hey I just noticed that my current power module has a different fuse size than my original power module. For those who know, what size fuse are you using for the fuel pump?

For the stock Ford pump they installed a 20 amp fuse. And contrary to replies here it was never run straight to the battery with no fuse protection. We ran into an issue with a recent build and it took going back into the Ford EVTM to find out that Ron Francis is not sizing their fuse to what Ford originally did. We explain it in this link:

https://www.youtube.com/watch?v=cMhRghg699U

[J R Jones]

Dave,
Thank you for the information and your history. You have a lot of history. In desperate times fraught with metaphorical alligators it can be hard to remember the original objective to drain the ....tank?
Threads bring to mind "The road to hell is paved with good intentions".
I found some good direction in your attached thread. Is there a filter for that?
jim