Madman_DSM

I'm starting starting a new topic because I've narrowed down the problem and the previous thread went nowhere.

So, the car is 95' Mustang GT, 5.0, manual transmission, VIN - 1FALP42TXSF206777
1) The car reaches 0-60 in 11 seconds
2) Air filter, fuel filter have been changed recently
3) KOEO test emits following codes:
Hard faults:
111 - OK
Memory:
181 (M) Fuel system was lean at part throttle Single, Right or Rear HO2S -
542 (O,M) Fuel pump open, bad ground or always on - -
4) KOER registers:
Hard faults:
111 - OK
Memory:
151 - ???!
5) Cylinder balance test outputs 9
6) Voltage at the fuel pump is 12V-14V
7) Stock fuel pump registers 2.0 bar (29 psi) at fuel rail (idle)
8) Evo fuel pump registers 2.1 bar (30 psi) at fuel rail (idle)
9) Stock fuel pump registers 4.5 bar (65 psi) at fuel rail (idle), return line blocked with finger
10) Evo fuel pump registers 5.0 bar (72 psi) at fuel rail (idle), return line blocked with finger
11) Fuel is pumped through return line just fine, at a very rapid speed
12) Tried to test the car with stock FP regulator (the one stuffed into fuel rail, connected to intake mani, bolted with two 6 side internal screws of size 5 Bosh, car run like crap even after I tested the second, supposedly good FPR
13) Car falls flat on it's face after like 2.5k RPMs
14) Engine pings
15) I'm afraid pistons are going to melt soon with that sort of lean conditions and pings, I'm running 93 (98 EU) octane to be on a safe side, but nothing can compensate the lack of fuel
16) No one has a friggin clue what the **** is wrong with this car, feels like a truck, goes like a truck and you can't even diagnose it!!!!!!!!!!!! No CELs, it's not an OBD2. There are no compatible surrogate OBD1 via OBD2 socket readers anywhere. No signs of ****ed up parts, nothing. It's the second week I'm spending more time in services than in my car, and that sucks ***, royally!

So please, can anyone tell me what should I do next?

I'm thinking about closing the frigin return line and take it for a spin tomorrow, I'm totally out of ideas.

P.S.: Previous thread - https://mustangforums.com/forum/5-0l...ml#post6555117

mjr46

how about listen, for one you were told that the obd 2 port is non functional on the 5.0 sn-95n stangs, the v-6 model was obd 2 compliant through that port rather than design 2 seperate harnesses ford used 1 for both. it will not work as a diagnostic port, how about clean the maf sensor, and do not block off the return!!!, tape a gauge to the windshield and read pressure under a full throttle stomp and see what the pressure does???

Madman_DSM

I'm sorry, I was venting at (16), it's two weeks going nowhere and just wasting ton of cash on different things and diagnostics. I did the KOEO/KOER tests, and they can't give me the data I want. And no-one has a logger to log that surrogate OBD1.
I know it's not, OBD2, and I wrote that it isn't. And I think you told me about KOEO/KOER, and that was very helpful, thank you, we avoided the extra work to remove exhaust manifolds today just because I managed to do the KOEO/KOER tests just before.
But still, it feels like running against concrete wall without a good data-log

I hope that someone has a gauge, because new one is ton of $$$ again!!! ...

But what does the MAF has to do with the fuel rail? The fuel pressure is supposed to be 39psi, but it's 29psi. No matter what the MAF says it's still going to be lean, won't it?

And the worst part is that I can't see one thing being wrong with fuel delivery...
Fuel pump voltage - Check
Fuel pump working - Check
Fuel pressure regulator - Check
Fuel line - Check
Fuel return line - Check

There are simply no more elements that could affect fuel pressure Ok, the fuel pressure could drop below 39 psi with some insanely big negative intake manifold pressure, but there is simply no way for it to happen...

mjr46

if you don't have the tools to verify proper operation you become lost like you are because you assume, get a gauge and test vehicle under load as I stated, plugged filter, or weak pump will manifest itself under load on the gauge, and the maf is what measures the speed at which air is entering the motor/intake and based on that the ecm knows what to calculate the inj pulse width at, if maf is dirty or snafu a lean calculation can be output, the ole addage, garbage in garbage out comes to mind., diagnostics begins with verifying and using the proper tools to do such and is not based on assumption.

Madman_DSM

We tested the fuel pressure with manometer at the service and it was accurate, but I can't use it while driving And I haven't seen an fuel pressure gauge that would bolt on to a Mustangs fuel rail.

mjr46

that test you did means nothing except that it is fine at idle, what about under lad???? huh???, fuel consumption at idle/rest is not under the same demands as load, just because pressure is good doesn't mean volume is good, ever seen the theroy behind a high pressure sprayer??? lost of pressure but volume is low.......until you do the test I have stated you cannot rule out a restriction in the fuel system or a weak pump, remember we're troubleshooting, not ASSuming and FYI gauges don't bolt on to the rail on the mustang, there is a schredor valve onto which a gauge screws

Madman_DSM

Emm, it's not fine under idle, the pressure is 25% lower than it's supposed to be.... The pump is fine, the pressure regulator is fine, tubes are fine, and the filter is fine. But pressure is lower than it's supposed to be. It's supposed to be 39psi at idle, right?

And if it's not fine at idle then at load it's crunchy piston melting goodness in there And I don't know how to fix it now

mattdel

39psi at idle with vacuum off and capped. equates to 31 psi with vacuum on. 39psi is full load WOT condition.

mjr46

listen to what mattdel said since you won't listen to me and want to ASSume all is well without running the tests I suggest, so whatever.....you know more than me FYI if you wish to fix the car the tests must be run under the conditions with which are in correlation with your complaint......just a thought, I mean if a customer comes into my shop and complains about a hesitation under acceleration, I don't sit in the bay and rev it up then say hrmmmmm no miss or hesitation...must be fine.....

Madman_DSM

31 psi with vacuum hose on? Then it might be that fuel pressure is correct. I was told it has to be way higher. I got 29 on vac connected, so I guess it could get as high as 39 at WOT. Service had an info it's supposed to be 60 psi at partial/full throttle, somewhere around 40 on idle.

Darn, no one here has a clue about how these cars operate And no manuals...

Testing was very simple.
Step 1: EEC test -> 2 codes relate to lean condition and fuel pump problems
Step 2: We took the measurement of fuel pressure at fuel rail -> 29 psi
Step 3: Call to people who work with American cars, they say around 60 psi is the average pressure.
Step 4: Fuel pump test/Voltage drop tests
Step 5: Fuel pressure regulator test
Step 6: Useless conclusions because of "step 3"

If the 31 psi with vacuum is target, then 29 psi is kinda close and all the conclusions we made today are wrong. But I can't say we didn't tried to do best we could based on information we could find.

Darn, I need to get a copy of the factory manual. No one here knows anything about these cars Not even a Ford dealership...

If the fuel assumptions about 60 psi operating pressure were wrong, then yes, MAF is the next thing that is suspect. I'll try to swap MAFs with donor tomorrow. But if it doesn't help then I'll be operating in a dark again I will try to do a stationery fuel pressure tests with vac hose closed to see if it reaches 39 psi too, but other than that... Next thing is the compression test on all 8 cylinders which is expensive... and out of ideas...

I could so use the manual

P.S.: mjr46, I'm sorry that I reacted the way I was, but I was working on contradicting information, you have given me a very valuable advice and I'm very grateful.