Injector Leak?

[JerrySab]

Hi guys!

The refinement process continues on my '88 XLT 2.9. Truck was left sitting for a week or 2 while i was replacing alternator and rewiring. WHen i started the project I found the top bolt at the exhaust header (#5 cylinder) looked damp. Pic attached.

About a year ago I replaced all of the injectors, which was a brutal learning process in finding and using the right injector. All was well afterwards though, and a misfire i was hoping to cure was indeed fixed. Now, a new gremlin, in the way of a periodically spiking tachometer and horrific mpg. This morning i did clear engine start routine and after a few turns, truck actually turned over. SO i believe this is a pretty clear smoking gun? It doesnt smell (like, really smell) like gas so my fear is that its coolant. O rings look fine there is not fuel on the plenum or on inhjectors themselves.

SO, question to the forum, would you also assume this is leaking injector? Would a damaged ground wire cause this to remain constantly open? Or is it more likely a mechanical failure with the injector? And finally, do y'all have any tricks to coax this thing shut while its still in the fuel rail? Or do i need to get back into the guts of this thing.

thanks

 

[Shran]

The way to check for a leaking injector would be to hook up a fuel pressure gauge, turn the key to Run (but not Start) a few times and then shut it off...just to prime the fuel system. The gauge should stay steady and not drop. If it does, you have fuel leaking past the injectors, fuel pressure regulator, or backwards into the tank. Regulators are pretty notorious for failing on these trucks and you can test by pulling the vacuum line off and seeing if fuel drips out. It is good to fix that immediately because it will fill the brake booster full of gas and ruin that too (had that happen a few times back in the day!) Usually a failed FPR also results in excessive cranking to start the engine when it's warm as well.

Failed coolant temp sensor can cause really poor fuel mileage too.

Not sure about the wet exhaust manifold, are you sure you didn't drip oil on it while checking the oil? I see that the dipstick tube is right there... pretty easy to do that

 

[JerrySab]

Quick reply thanks @Shran.

I feel pretty good about fuel pressure regulator, it's not and not the crappiest version. The previous version was absolutely toast, and exhibited all the signs you mentioned. NOT SURE ABOUT THE BRAKE BOOSTER THOUGH YIKES

It's def possible i got careless with the dipstick lol

the way the fluid seems to be seeping out of that upper bolt in particular is my main cause for concern. I just changed oil and theres no milkshake. Im not noticing significant coolant loss either. so i blame injector. The stain is no longer there now that im driving truck again.

i'll see about a fuel pressure guage thanks man.

 

[JerrySab]

Also, can a pressure gauge be installed on the schraeder valve on the fuel rail, and just live there?

 

[rumblecloud]

Absolutely:

You'll most likely have to do a little custom fitting, but it's a thing. I'm gonna do it soon as the weather decides what it's going to do.

 

[RonD]

Try the "Clear Flooded Engine" test

Turn on the key
Press gas pedal down to the floor, and hold it down<<<<this turns OFF fuel injectors
Try to start engine
It should just crank and not fire
If it starts then you MAY have a leaking injector(read at the bottom)

I do this every morning when starting my high mile 4.0l(400k) to get oil pump thru the engine before I release the gas pedal and it starts

When computer sees WOT(wide open throttle) at 0 RPMs it will not pulse(ground) the injectors, so driver can "Clear a Flooded Engine"(dry it out), all fuel injection computers have this, not a Ford thing

If engine started, then you MAY NOT have WOT
Press gas pedal down to the floor with a stick against the seat
Go to the engine and see if you can manually open the throttle a little more, if so Google: Ranger throttle cable mod

If you have WOT then disable spark, pull the coil wire to distributor
Cycle key on and off a few times
Do Clear Flooded Engine again, and crank it a few times with foot to the floor
Now start pulling out spark plugs, the one with the WET TIP is the one with leaking injector

 

[JerrySab]

OK I feel really stupid now, but here goes:

Disclaimer, every time I believe I fix something, another thing breaks in the process. I love and hate this truck.

I think there's a catch in the gas pedal, something that prevented WOT. or TPS is out of range. Either way. While attempting CFE test, the engine not only turned over but damn near redlined because my big dumb foot was still on the gas pedal.

And now I have new electrical problems. I didnt find any cooked fusible links or fuses (yet), but now there is pronounced weakness with electrical components when rpms are low. even turn signal blinking is glacial. Ive had an old ass g2 alternator and never had this issue. I did upgrade to Motor City Reman 175 amp alternator recently, and i either killed it or it killed my components. OR there's a smoking gun (or wire) buried in the loom and I just havent found it.

Truck still behaves like an injector is misbehaving, havent cracked off intake plenum yet to root around. ran a can of seafoam (lol) through the tank jsut for good measure. But curious if wiser minds have insight on me potentially frying my brand new alternator.

 

[RonD]

Not at all uncommon to lose a Field in an alternator, new or not

Alternators have 3 Fields in their outside case, basically each is a large coil of a single wire, so 2 ends
As the Rotor spins each Field generates AC voltage, each Field has a set of Diodes connected to the 2 ends and they change the AC to DC volts and that's what comes out of the alternator
Each Field represents 1/3 of alternators capacity, but its actually more than a 1/3 because alternators can't generate full AMPs all the time

An alternator's AMP rating is based on engine RPMs at a minimum of 1,800 or 2,000, so not at idle, 650-750rpms
If a Field(or 2) should fail you would only notice that at idle, common sign is dimming head lights or dash lights at idle, no that is NOT normal on any vehicle, lol

Break out the volt meter, test battery voltage, engine running at idle, should never be lower than 13.5volts, warm idle is best, lower than cold idle
Then test at say 2,000rpm steady
Should be the same as Idle voltage, that's the point of the Voltage Regulator, generally just after startup you would see 14v to 14.7volts
Then after 5 minutes or so, battery will be re-charged so 13.6v to 13.9v, just under 14volts
Over 14volt long term can "cook" a 12v battery

If there is a big voltage change between idle and 2,000rpm then alternator is for sure the issue, new or not it has a problem


As for the WOT, you need to test if you are getting full throttle via the gas pedal/cable
Key off
Use a stick against the seat to press gas pedal to the floor
Open hood and see if you can manually open the throttle a little more
If so, Google: Ranger throttle cable mod
easy fix
And engine will be more "peppy" if you get full throttle back

 

[JerrySab]

So, huge thanks you guys and RonD as always. Still pecking away at the issue. Alternator was not OK, so sending it back and have already replaced with a reman 3g from a mustang. Great. I definitely notice a drop, albeit brief, in RPM when turn on an electronic. Headlights. quickly sling the fan to full blast. Is that part normal? I ask because the voltage sense wire runs to fuse box. I believe. But I have seen other diagrams where the voltage sense wire goes from voltage sensor to b+ post on alternator, 3" away. Which is the more efficient wiring route? Battery light comes on at key-on, so not worried a ton about wire path, just wondering what most efficient set up is.

Also, linked up a few zip ties at pedal, love that fix, going to dive back into injector tests next. Thanks everybody.

 

[RonD]

Yes, depending on the alternator, there would be a drop then return in RPM at idle when you turn on a larger amp draw, like head lights or Blower, normal

Yes, there are several ways to wire in an alternator, the B+ wire(s) should be fused or fusible link to Battery Positive, in older Fords that was to the Starter Relay(solenoid) larger post that has Battery Positive cable as well as several other wires
That post is the 12volt power distribution point for the whole vehicle

Fusible links were used because they are easier to wire in AND they are "slow blow" fuses, they will tolerate brief voltage/amp spikes without blowing

The yellow wire on the regulator, voltage sense wire, can be hooked to B+ with a 15amp fuse or fusible link and it was done that way in many years, but in the harness not usually on the back of the alternator, lol

A separate 15amp fuse in engine fuse box was used most of the time for yellow wire

B+ and the yellow wire are BOTH hooked to Battery Positive full time via a fuse or fusible link, so electrically they are connected to the same place

Green wire is the Battery Light, also the ON/OFF switch for the alternator


One wire Alternator's use a centrifugal/RPM switch for ON/OFF
B+ and yellow are combined inside alternator, so just need the one "fused" wire to Battery Positive
The "green" wire is also internal, uses the 12v at B+ but thru a centrifugal switch
When alternator starts to spin centrifugal switch closes and sends 12v to voltage regulator which turns ON the alternator

Why don't car makers use One Wire Alternators, seems so simple?
Because they don't work well at low RPMs, i.e. idle, they can switch off and on
But they are very cool to use in custom wiring, ONE WIRE, very cool and easy to wire in

 

[JerrySab]

Ok, back again after nearly frying my truck. Ditched the MCR alternator and went with reman 94 mustang. All good there, super appreciate all of the collective wisdom here. Happy to have a working part again. After swapping the alternator I finally had time to do some fuel pressure testing, and it's not looking great.

ATtached guage to scharder valve at rail, pressure is 0.
KOEO was able to prime rail to 38psi, where it would quickly fall to 32 and remain there, then slowly fall.
KOER / cold = 30psi.
KOER + gas pedal = no affect on pressure. 30ish.
KOER + removal of FPR vac line = 40psi steady. restoring vacuum, drops to 30ish.
Overnight, pressure fell from 32 to 0.

I did not pull any plugs yet to see if any are wet/clean, but i have to imagine this is coming from a failed injector? FPR seems to be doing its job correctly. I know there is a check valve on the high pressure pump that can stick open, but if that were the case, I feel like I wouldn't see 40psi with engine running and vac line pulled. Is that a correct understanding? I just want to make sure I'm going in the right direction before i spend the time yanking off the intake plenum and rail.

Thanks guys!

 

[Shran]

The high pressure pump is capable of way more than 40psi, the regulator just does its job and dumps excess fuel back into the tank.

You should be seeing around 32-25ish PSI at idle and up to and right around 40 under low vacuum conditions (watch the gauge and crack the throttle open briefly - like open it and let it snap shut right away.) Not seeing an increase there with that test would usually indicate to me that the pump is not working well...but if you are seeing an increase with the vacuum line removed, you should check over the vacuum line going to the regulator to make sure it's not partially plugged, melted, kinked, etc, then suspect that the regulator may be faulty. You did replace that, right?

The falling pressure thing is a different issue entirely. It is not supposed to do that. Should hold pressure indefinitely. My gut feeling is that you have a weak high pressure pump in addition to something going on with the regulator or vacuum lines.

You could test the pump by removing the feed hose from the fuel rail and plumb it directly into a fuel pressure gauge... see if it maintains pressure there or not with the rest of the fuel system removed from the equation.

 

[JerrySab]

Damn. Just as soon as I think I’m getting close. Watching the pressure fall was pretty disheartening.

FPR is new. All symptoms point to failure there but vacuum line could be at fault also. The line is soft and longer than I would expect, as it’s only going like 3” away. It looked like it was pinched in the spark plug wires by distributor. I can redo that test easily.

So if an injector is stuck open, it wouldn’t piss gas into combustion chamber when truck is not running?

High pressure pump looks old as hell, I wouldn’t be surprised if it was underperforming. If I were to disconnect feed line between fuel filter and rail and block/pinch it off, and IF the high pressure pump is the source where pressure is bleeding out.. then I would see consistent pressure at fuel rail right?

 

[Shran]

If an injector is stuck open you will have a horrible miss, severe lack of power and it will probably smoke really bad and may be hard to start, especially when warm. I kind of doubt that is the case here but it's possible... would put that dead last on your list of things to check.

High pressure pump looks old as hell, I wouldn’t be surprised if it was underperforming. If I were to disconnect feed line between fuel filter and rail and block/pinch it off, and IF the high pressure pump is the source where pressure is bleeding out.. then I would see consistent pressure at fuel rail right?

You could just remove the fuel line from the filter... the side facing the front of the truck and hook your gauge up there then prime the system and watch the gauge. I don't see any need to pinch anything off, you just want to test the pump by itself and rule out fuel leaking past the injectors into the engine or the regulator into the fuel return line.

 

[JerrySab]

Ok, so doing preliminary pricing of pumps in case my current one is busted, realizing I dont know much about flow rate.

Should in-tank pump and high pressure pump have matching flow rates? Is higher better? I'm seeing a decent amount of variation, some with 15GPH and others with 40GPH.