Fuel pump, or pumps, or....

[milehighXR]

Continuing to diagnose code 42, and overall poor idle, today's results so far:

OTC fuel pressure gauge installed, jumpered relay terminals 87 and 86 at fuse panel socket to rule out bad contacts at relay, or weak relay. 39 to 40 psi at rail in under 2 seconds at KOEO. KOER idles a little better than last week, and I detect a miss still(this seems like this engine has always had a miss, even with new wires etc, and post rebuild way back in 01, have new magnecore wire, and new cap and rotor, and fresh now). Run at 2000-2200 rpm to get hot and miss, or popping(for lack of better term gets worse). 32psi at the rail and about 8-10 in hg vac on boost gauge.

Next fuel volume test KOEO, performed 3x, and also once with external filter bypassed. Less than 4oz everytime. So I either have clogged fuel lines(not likely, none kinked that I can see) or one or both pumps has gone bad.

I see no diagnostics for the individual pumps in the service manual. Does anyone know how much volume the stock low pressure pump should flow to the external high pressure pump?

I'll start taking the tank down and finish inspecting and blowing out all the lines. I assume that when we go to the Walbro high pressure in tank pump we just sub a 2nd fuel filter in place of the external pump? I almost put a Wlabro in back in 2017 when I found the in tank pump bad and didn't do it. Can't remember why, but I think that the Wlabro 255 was scarce, or at least not available from Napa.

[milehighXR]

Also is the fuel pulse dampener really needed? I just wanna isolate potential clog points.

[milehighXR]

Finished working on the car earlier, just now got to posting remaining results:

No kinks in any of the fuel lines from rail to high pressure pump. No clog in that line, or the pulse dampener either.

Low pressure pump, I made a handy-dandy gauge shut off drain unit for lack of better term:



I had 2psi, and 8oz flow over 10 seconds. I'm guessing that probably low?

Next, similar different setup for the high pressure pump, even though I had 39-40psi at the rail with this, I still wanted to verify flow with this pump on its own. It flowed 12oz at 80psi(it was powered straight off the battery).

So it looks like the fuel tank comes down next, and I inspect the remaining fuel lines that I can't reach or blowout before I disconnect the remaining fuel pump. I just can't see anything else to do at this point. I really wish the service manual had diagnostics for flow rate of each individual pump, as I really don't wanna replace potentially good parts. I just put the in tank pump in back in 2017... And I'm pretty sure it was for the same reason.

[my8950]

I don't believe there is any information on the individual pump, since they both either run, or don't run. The system is not set up to run just one.
The pulse dampener is not really necessary, many have removed it and not had any issues.
I'm not understanding why you test hooking the pump directly to the battery when it does not run like that in the car, I'd think that is possibly introducing another variable.

If you're dropping the tank, install the Walbro 255lph High pressure pump, order from MC2, install new fuel filter and be done with it.

[milehighXR]

I understand they don't run independently by design intent, however the Ford diagnostics take great pains to avoid replacing otherwise good parts. I'll be buying the Walbro as soon as I get the tank down, I just really wanna know the in tank pump is bad before buying a new one. And I'm still missing something, because I'm not really understanding why it would be causing a rich condition... Fuel system does not leak down when pressurized, not even after 5 min...

[my8950]

True, from looking at the info you post, it has good pressure, maybe the volume is low.
When you drop the tank, check the screen of the pump, or the tank, maybe it's full of barnacles like mine was.

[milehighXR]

There won't be much in the way of barnacles, tank was sent out in 2001 to have the inside flushed, cleaned, and then was coated inside and out with a rubberized coating. I had been sitting with less than full tank of fuel mi for 5 years, and it was nasty.

I plan on checking the screen, and maybe even using my inspection camera to verify the screen isn't smashed by the coating...

[andyofcolumbusmerkur]

There won't be much in the way of barnacles, tank was sent out in 2001 to have the inside flushed, cleaned, and then was coated inside and out with a rubberized coating. I had been sitting with less than full tank of fuel mi for 5 years, and it was nasty.

I plan on checking the screen, and maybe even using my inspection camera to verify the screen isn't smashed by the coating...

A rubberized coating? I would wonder if the in tank filter or the main fuel filter was clogged. If you are dropping the tank you might as well do everything from the tank forward. I have heard you don't need the pulse dampener but I prefer to leave it there since it was put there for a reason. I wouldn't care if it was installed or not however when running the 255L or similar. Lot's of people use those types of pumps and don't have any type of dampener.

[milehighXR]

In tank filter was replaced in 2107, external filter at eh same time. Fuel pressure testing was done without the external filter to eliminate that as being clogged.

I have a Walbro on order with MC2 now. Hoping I get it by friday...

[my8950]

In tank filter was replaced in 2107, external filter at eh same time. Fuel pressure testing was done without the external filter to eliminate that as being clogged.

I have a Walbro on order with MC2 now. Hoping I get it by friday...

I would still check it. You may have to replace the filters a few times before 2107 depending on if we still can use gasoline for our cars.

[thesameguy]

Random things:

The pulse dampener is there to eliminate resonances created by the opening and closing of the injectors. It was a big part of '80s EFI but largely doesn't exist anymore. I don't know what changed, if anything. It's possible everyone just came to the conclusion it wasn't necessary and better to save the money. Mine left with the factory fuel pumps a decade ago.

When you install the Walbro you just use one filter to connect the incoming with the outgoing fuel lines. They will bend adequately.

Typically fuel pump flows are only measured unrestricted... The 255 only flows 255lph at 0psi. I've never seen a factory test for a fuel pump where the fuel pressure regulator is involved. You must volume with an open line, then pressure at the rail.

Not enough pressure causes a lean condition since injector openings are calibrate for a known relative pressure. If pressure is low enough that atomization sucks you can get a very lean condition as the plugs fail to ignite a bad mixture. Not enough volume is a different condition... That's just lean running. I've never seen a too much pressure problem... I don't think an FPR can really fail that way.

[milehighXR]

The pressure measurements i gave are with the gauge valve closed. Then open gauge valve and look at volume.

Walbro is on the way from MC2 now. Hope i have it Friday.

[milehighXR]

Got the Walbro in. Fuel may or may not have been the issue, but it was a worthwhile, and long overdue upgrade. Instead of using another fuel filter to take up the space vacated by the external pump, I was able to position the lines to connect to the existing fuel filter with minimal fuss. I need to go back and heat up the line to bend it so it's not stressed, but this works for now. The external pump wiring has been clipped off, taped and tied off to the filter bracket so it can be restored if desired.



I should be ready for smog now. I'm not really sure what is going on, but even after the fuel pump change, I still had code 42. Blocked off EGR and reran test, no more 42. Found a vac check valve laying around, installed it, and removed EGR block off plate, and still no code 42. I had thought that the EEC(8UA) did not command EGR at idle. Unless I have a leak thru the EGR solenoid, but when I remove the vac line from the EGR there is no change in engine RPM. Next step is to fix the turn signals again, get temp tag and get smog test. I hope to get that done this week, well see, our county has become a fascist fantasy land, and is imposing stricter covid protocols than the rest of the state for no reason at all. I may have to make an apointment for the temp tag, which could take a week or to before I get to actually go in...

[thesameguy]

I think we have forgotten what fascism actually is.

[andyofcolumbusmerkur]

Where I live they closed the dmv for a short time, and let people drive around with expired tags. When they opened they limited the number of people that could be inside at once, and had everyone else wait outside spaced 6 feet apart. I used the self service (outside) kiosk to get the echeck on my Mom's newer car, but nothing I own needs echeck anymore. And the Merkurs have Historical tags which are good for 50 years so no worries there. They even changed from 2 plates to just one plate. Cars look so much better without that front tag in my opinion.