Fuel pressure regulator issue?

[GoodSamaritan]

I've had the HillbillySUV sidelined for a few months, although I have used it around my property, started it every couple of weeks to run for a few minutes.

Yesterday was the first time I'd driven very far in months. I noticed right away it wasn't running as it should, but chocked it up to old fuel and sitting too long.
Even with fresh fuel it continued to run worse, eventually stalling out multiple times as I pulled up to a stop light.

By the time I got home it was surging pretty noticeably and had a bit of a miss. Also it smelled as if it were running too rich. My first thought was that I the one of the stock O2 sensors had crapped out. On a whim I thought I'd unplug the injectors one by one to see if that made a difference.

To make a long story short, the thing idles better with all 4 injectors on the drivers side unplugged. Removing the vacuum line from the fuel pressure regulator and it doesn't seem to make any difference.

After turning the engine off for a few minutes I still have pressure at the test port so I don't have an injector stuck open.


I ran the codes and it came up with a bunch of emmissions codes (stripped off the engine years ago). The lone stand out was a 42 indicating a rich condition at the O2 sensors. (duh)

I'm left wondering if the O2 sensors are shot, or if the rich condition is the result of something like a bad fuel pressure regulator feeding too much pressure to the injectors.

Any ideas?

[VicCrownVic]

At first I was thinking split in the hose between the pump and outlet on the hanger assembly. The more I read the more I'm not sure about that.

Do you have access to a fuel pressure tester or would an auto parts store have one you can rent? Sounds like you will want to start by getting a pressure reading and go from there.

Also, I know my FPR has a vacuum line that connects to it. I'm not sure what affect a vacuum leak would have but it would be good to check since that would be an easy fix.

[Tiggie]

May want to make sure mice haven't made a nest in the air filter housing or throttle body.

[Rodentkiller]

GS test for an Intake Manafold vacumn leak my car ran like crap and I got out my scan tool and it showed all kinds of codes like an O2 sensor acting up so this is a suggestion.

[gadget73]

Check the vacuum line to the MAP. If its good, try unhooking it to see if it runs better. Bad MAP sensor runs like no vacuum to the MAP, which is stupid rich.

Weak fuel pump or fuel pressure problem usually shows up as running very lean. Might be worth pulling the vac line off the FPR just to see if its spitting fuel though. If its not, then the FPR probably isn't shot.

[GoodSamaritan]

There is no fuel coming out of the regulator, and the line going to it has vacuum at idle.
By the time I thought about getting the fuel pressure tester the auto parts store was closing so I'll have to pick one up.

Gadget, I never thought about the MAP sensor but I can pull one off the Lincoln and swap them to see if that helps.

[gadget73]

Sensors rarely die, but it happens. Bad vacuum line to it is slightly more common. Either way, its simple enough to try if you've got a good running car to borrow from.

[GoodSamaritan]

I finally got a few minutes free on sunday to poke around a bit on the HillbillySUV. I still haven't gotten a chance to check the fuel pressure, but I did check the vacuum line going to the map sensor. It's ok and the car dies almost immediately when the line comes off. I did find a small vacuum leak on one of the lines coming off the vacuum tree behind the upper intake but nothing else so far.

One thing I did notice was the front injector on the drivers side doesn't seem to be cliking. I can sorta feel the injectors firing when I touch them but not that one.
It's subtle but and probably more than half imagination but it makes me wonder if it's staying open when the key is on. I know I still have pressure on the fuel rail several minutes after turning it off, but I'll have to see if it drops with the key on.

[gadget73]

unplug the injector and see if the idle changes. Thats how I've confirmed dud injectors in the past. That and a rubber hose jammed against the body as a stethoscope.

[GoodSamaritan]

The idle doesn't change at all with that one. There might be a slight difference if I unhook the one next to it but if I unplug all 4 of them on that side it actually smooths out. I'm beginning to suspect something is keeping one or more injectors open 100% when it's running.

I'm tempted to swap ecm's but I don't want to damage anything if there's a problem with the wiring harness.

[gadget73]

The ECM rarely is a problem, though we are talking 30 odd year old electronics now. I have re-capped a couple of them, but despite having green fuzzy caps all of them were pulled from running cars. One thing I have to credit Ford with, they built an extremely reliable computer. There are only 3 parts on it that are particularly prone to age related failures, and it took an awfully long time for them to start having troubles. They're also cheap and readily available parts, around $10 total.


Pull the plugs, that will tell you if one is stuck open.