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Discussion Starter · #1 ·
Hey All,
I have been battling an intermittent no start issue (when temp < 35F). Even when it does start and run fuel system drops to 0psi as soon as care is shut off. Have done lots of multimeter measurements and previously replaced parts (Pump, Filter, Fuel rail pressure sensor). Power and ground are good to fuel driver module and pump.

One question, on the returnless system I believe fuel pressure regulator is built into the pump, correct? I see this one part(see pics) in the fuel line prior to fuel rail sensor. It just has incoming and outgoing fuel line, no vacuum line or anything else. Does anyone know what this part is? I can not find anything calling it out in Ford Service manual or anything on internet. Would like to know what it is and what it does.

I really do not want to throw another fuel pump at this as the condition has come and gone prior to replacement of pump. There is something I am missing but can't figure out what, If anyone has any ideas on measurements to check driver and pump out that would be great. From what I can see the communication signals between fuel rail sensor, PCM, Driver Module and Pump are accurate to what fuel pressure is. Meaning low Volts when 0psi and up to 2.8volts when car starts and runs (39psi)

Thanks


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I think that's just a pulse damper.
Tell us more about your symptoms.
 

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In returnless systems the ECU controls the fuel pressure by varying the voltage to the pump depending on what the fuel pressure sensor is reading, therefore I don't think they actually have a regulator at all.

This only happens below 35F?
 

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Discussion Starter · #4 ·
Ok someone else responded about a pulse dampener on another forum, still can't figure out what it does and internal mechanism and if it could be a cause of zero fuel pressure.

Here is long back story of what's been going on for last 4 months: Car has been in family since new, but I took it over July 2021from a family member, Car ran good through November then started having no start issues seemingly only when cold. If car sits for several days after a no start or if it warms up (over 40F) car usually starts. Ignition Has good Spark, put in new plugs and wires. Good Cam and crank sensors. Replaced fuel pump and fuel rail pressure sensor. Fuel Pump Primes always but many when not starting it builds pressure builds ONLY when I cycle key on 5-10x. It still won't start usually as it seems flooded at this point. When car happens to start fuel pressure starts at 0psi but will build while cranking to 40psi. but Fuel pressure ALWAYS drops to zero as soon as car is turned off (true if crank no start and when it runs). On warm days when car starts it is running really rich (LT Fuel trims -20+). Before diving into electronics I thought I was getting stuck open injector. This weekend I verified injectors are good, no leaks under pressure and all fire as expected when rail pressure is > 30psi

So here is data I have:
Fuel rail Pressure transducer Sensor - 5V ref is good, ground is good, signal line voltage seems to be normal reads 0.47v when 0 psi and about 2.75 when pressure is at 40psi. Signal is good all the way to fuel driver module

At Fuel Pump Driver Module: (comparing values to Scanner danner video): Inertia Switch voltage supply is good 12V, Grounds are good. The power and grounds are also good at the Pump. One issue I see is 2 signal wires values I believe. Pin 1 (Ground/Switched) - KOEO (0V) Cranking (2.7v) when turn key off goes up to 3.3V then to 0v. Pin 7(Voltage , Ignition switch in start or run (not overload protected), switched) - expected square wave 0-5V, getting square wave 0.4 - 2.3 volts)

After 4 days of not starting temp warmed to 46 deg F Sunday and I got car started. It then would not run today (Tuesday but it's still 45 deg F so maybe temp is nothing )
Here is info I collected when running I was monitoring Fuel Pump %, Fuel Pump Monitor %,Fuel pulse width FRP (v) and FRP (psi)
At crank, 0 FRP (psi), FRP (v) 0.52, FP% 75, FPM%,- 98-100%
As engine started RPM went to 1900 FRP - 39psi, FRP(v)=2.79, FP% -19, FPM-96%
From there I noticed that the FPM% bounced between 90-114%, over 100 most time, pressure stayed constant at 30-40psi and FP% was 19 and FRP(v) was 2.74

The no start condition keeps happening consistently (every week or two) even thru all these part changes, It might start after a "fix" was made but really I think it just started because vehicle sat for X amount of time. One theory floated from other videos is when I replaced pump and not filter, if filter was blocked I could have caused damage to new pump by creating too much pressure on it. I don't get what could fail inside the pump though and only be intermittent. After talking to my family that had it before me they said they noticed this same kind of no start but thought it was from sitting too long . It was an extra car and would sit in garage for months between use. If it started they might drive it if it didn't they would not Obviously they did not put much thought into what was happening

Long post I know but I'm running out of ideas. Good news is weather is finally getting warm so maybe it will go away until next November . Kidding I want this fixed, but as weather warms I am concerned that it "self corrects" and I won't know if it's truly fixed.... Hope this made sense.... trying to put 4 months of struggles into a message

Thanks for taking time to read.
 

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Where in the system is your pressure gauge installed at?
 

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Discussion Starter · #8 ·
I put the pressure gauge on the schrader valve, which from memory is post the fuel rail sensor. I also used forscan and it has matched pressure of gauge, Both when no pressure and when running at 40psi.

I've read people having issues with cracked /split lines between pump and outlet of tank. I won't say I looked very close at that when I replaced pump. I think when I get home this weekend I will run an air pressure test from pump line to fuel rail, If I pressurize to 40psi (same as fuel pressure when running) I would have to see a fast leak , If not I guess there is a check valve internal to the pump that would be source of leak?? . One of those 2 have to be source of leak down.

As I think about it having that much of a leak (falls to 0psi within 2sec of shut off) that has to screw all my ST and LT fuel trims up,,,at least that is my current theory LOL
 

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In the last few years I've found that I need to pause between run and start for a second to prime the line whereas I didn't have to do that before. I've replaced the pump in the last year or so but that had no effect on the need to pause. Since its an easy workaround, I haven't really put much brain power into it but now you have me wondering if there's an inline check valve somewhere that I've missed noticing.

Regardless though, you should have no problem priming the line once the key is turned so the problem is still strange. Your statement that it acts flooded and runs rich really makes it sound like an injector problem. Since this is an intermittent issue that may or may not be related to temperature, its possible that your injector testing was not conclusive.

I would replace injectors. It shouldn't be too hard to find a set for cheap either here or on the facebook group. Even a junkyard would work although they would probably be a little more expensive that way.
 

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Discussion Starter · #10 ·
I feel confident it's not an injector issue, I had the whole system hooked up and pressurized with fuel (via KOEO cycling) to 40psi. Did this by pulling the connectors so they could not fire. The system leaked down immediately and not a single drop of fuel came out of the 6 injectors, with the connectors hooked up all 6 fired as expected and no leaks from any on Key off.

Supposedly there is a check valve as part of the pump assembly, I have the old one in garage and will look at it more closely. Since I changed fuel pump assembly (not just the motor portion) and condition remains unchanged after replacement doesn't make sense I would have two pumps with bad check valves, not likely.

I am now going to approach as 2 unique issues, solve the leak down issue first as I think it's easier to identify. Then see how vehicle is running and work on air/fuel issue.
 

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Discussion Starter · #11 ·
Posting an update and looking for advice:
I put in new fuel pump and it did fix the fuel pressure issue, the fuel pump pressure relief was stuck open (luckily was replaced under warranty as it was 1 month old) , Once replaced FP was at 70psi Key on and when vehicle started it would remain at 4=38-42psi... so no FP problem solved! However, vehicle still will not start regularly when cold (sub 40deg F)

Then IAC and MAF
I did some more analysis and out of frustration threw parts at the car. I noticed if I manually cracked throttle body plate I could get it started. Replaced IAC thiking this was at fault.... no change! Then from youtube saw idea of unplugging MAF, won't start plugged in but starts everytime when unplugged. Seemed reasonable to be a MAF issue, replaced it.... Now still will not start when cold.

Any idea what could be left as possible cause of vehicle not starting when cold but starts if MAF is unplugged?
Once started and MAF plugged back in runs like a beauty. Vehicle will also start like new until cold soaks and is cold outside.

I was googling and came across some ideas " This has to be checked when the car isn't starting. With a voltmeter, check any fuses marked PCM, BCM, IGN for 12 volts. My suspicion is ignition switch or fuse block, both are common but ignition switch is much more common. PCM IGN, F/P INJR, PCM ACC and IPC/BFC ACC fuses are all fed from the ignition switch."

Anyone have thoughts on how to proceed? Next steps are looking through some electrical schematics I guess
 

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Unplugging the MAF simply makes the ECU default to a fixed set of "safe" fuel tables. RARELY does the MAF sensor ever fail.

Since this is so temperature-dependent, have you tried any troubleshooting steps on the IAT and/or the coolant temp sensors?
 

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Discussion Starter · #13 · (Edited)
I should of asked before shot gunning part MAF replacement ! I have not done any specific actions on the temp sensors because on all my FORSCAN logs the data (Intake and ECT) has made sense, matching ambient temps and climbing as expected. Any ideas on what to look for beside accurate readings?

One thing that I noticed last night after MAF replacement, It seems the thermostat went bad (2nd time while working this issue) The ECT went up to 230F+ and had no heat in car after 15 min which normally I would have heat. Coolant was definitely not cycling thru rad (hoses cool to touch) as I think about this I have a Failsafe thermostat from when I swapped out prior, so it should fail open. Prior to this I noticed the cooling fan was running on high 100%. I need to look at this more systematically I keep burying my head chasing a specific issue and lose sight on what ese is going on. LOL!
 

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... It seems the thermostat went bad (2nd time while working this issue) The ECT went up to 230F+ and had no heat in car after 15 min which normally I would have heat. Coolant was definitely not cycling thru rad (hoses cool to touch) as I think about this I have a Failsafe thermostat from when I swapped out prior, so it should fail open. Prior to this I noticed the cooling fan was running on high 100%. I need to look at this more systematically I keep burying my head chasing a specific issue and lose sight on what ese is going on. LOL!
This sounds like a leaking seal on the water pump.
Does the heat work at higher RPM's?
 

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Discussion Starter · #15 ·
Back in Dec I had no heat due to bad thermostat, I replaced the thermostat and no heat issues prior to yesterday . There was no heat at any RPM yesterday, feel confident thermostat did not open as hoses were cold to touch out of radiator and hot (230+) at engine.

I will take a more detailed look at things tonight as I have been rushing judgements due to lack of time. I have been looking at this thing for 4 months off and on but need to get it running (well starting regularly ) need the vehicle for kids this summer. That being said if my theory (based on issue onset and when it starts doesn't start) holds true the warmer temps will eliminate this issue soon, well until next fall. This weekend is getting into 70's so can see if it fails to start at warmer temps
 

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Take a close look at the bottom half of the water pump casing. There's a tell-tail drain hole there. If you have a snail-trail leading from that hole, than the seal is bad.
 

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It might be worth the trouble to do a compression test both hot and cold. I've never done it on this car before, I imagine it might be a PITA for bank 1, but I could see a small leak in the head gasket causing these symptoms.
 
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Discussion Starter · #19 ·
Thanks for the PCED link, I had been looking for a copy and should have bought this months ago. I will tear into this this weekend hopefully. I did look at the water pump and no signs of leaking at all. I will hold off on compression testing just due to difficulty for now. The other reason is vehicle runs great once it starts , haven't seen any sign of problems other than the no start when cold. For now, I am going to try to chase it as it's some electrical gremlin. Thanks again for taking time to offer up ideas
 
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