fuel pouring thru #5 bleed line and rough smokey idle

[kls2020]

97 Mercury 200 EFI # 0G457599

Been going thru motor to update with new parts and won't idle down and have to open throttle plates slightly to keep it running .
Steady heavy stream of fuel observed flowing through tygon bleed line for # 5 cylinder only . Injectors cleaned and flow tested . New reeds installed . removed plenum cover and powered up fuel pump to look for fuel rail/injector leaks . Rail pressure 36 PSI no leaks anywhere . Pulsed all three injector pairs using analog EFI tester and all looked the same as far as pattern and were closed when switched off . I can't think of anything that would explain where all this extra fuel is coming from other than a problem with injector 5 . What else could cause this gushing bleed line ?

[EuropeanAM]

Check for fuel flooding out of VST (Vapor Separator Tank) into the bleed system, due to needle/seat/float problem.

[kls2020]

Pumping up the fuel system with a remote tank the bulb gets hard where you can't pump it anymore . I looked closely at all of the bleed lines when this is going on and the flow is definately "out" of the # 5 bleed fitting and not the VST return line . I am going to try tomorrow cranking the engine over with the plugs pulled /grounded and try to see what the injector spray patterns look like and if any are failing to close properly . I am also going to put a dual trace oscilloscope on it tomorrow and check the timing signals from 1-3-5 coils to the ECU and the injector pulses and compare .

Thanks for the response.

[lpugh]

Have checked the injector control side for shorts to ground as the would cause the injector to be constantly open when running, with key off there would be no power so the injector would then seal indicating no leakage, The lab scope will tell you if this is the case as it will flat line low voltage on the control side

[EuropeanAM]

+1... and if it does, check the harness inside the intake carefully (wires sometimes get pinched between the cover and case, or abrade against the case near the bottom).

[kls2020]

OK I turned on the key to pressurize the fuel rail ahead checking the injector pulses with the O-scope and pressure was not making it up to 35-36 psi before pump shut off after 30 seconds (something I had never seen it do before ) I pulled the regulator and put over a container and turned the key on and observed it bypassing fuel pressure well below 35 pounds (20 psi ) and after a couple of attempts the fuel pressure won't climb above 10 PSI at the schraeder valve and fuel is spraying heavily into the container when the pump is running . I ordered a new pressure regulator and continued on with my testing . The waveforms I got cranking the engine over monitoring the injector pulses were all identical between the three injector pairs a quick spike up and then an opposite going quick spike down . I am assuming this negative going spike is closing bias to quickly seal off the injector? Checked the injector wiring inside the plenum for pinched or damaged insulation and it all looks good . I checked (ohmed ) every pin on the female plug to the ECU back to the opposite end on the engine harness (plus insulation to ground) and recorded the readings and that all looks good too . I am hoping this rich idle condition I've been battling is because of the fuel pressure reg was going south .

[Nova Kaw 650]

What does the #5 plug look like? Is there fire in that cylinder?
I'm not familiar with this engine set up; can you swap the injector to another cylinder?

[kls2020]

All of the plugs look the same . Performed ohmic and cranking voltage test on stator and trigger windings = good , pulled flywheel and inspected for cracked or loose magnets found none (compass moved around inside of flywheel showed 6 north and 6 south poles equally spaced), 2 new sierra switchboxes and 6 new sierra spark coils, spark box lit up like a Christmas tree when cranking over .
I don't think this is a weak or lack of spark issue .

[EuropeanAM]

Spikes you saw are from the collapsing field when you remove power on the winding. That's normal (though you're not observing function at any real running RPM range in real time, unless it's dampened heavily).

Your Regulator was likely bad. The continuous drops in pressure with pump running was likely due to the fact that you had expended the fuel in the VST, and were running the pump DRY.

None of this is likely related to your original complaint, BUT this should be addressed BEFORE doing anything else (address the OBVIOUS problem before searching for the obscure one).

[lpugh]

Pull the small line off of the pressure regulator while running to check for fuel coming out of the regulator, should be none, also trace this line and tell us where it is connected on the motor

[kls2020]

My original goal of testing last time out was to observe all six injector spray patterns cranking the engine over but since I did not have the required fuel pressure to the fuel rail that was a bust so I just looked at what I could . New regulator is supposed to be here day after tomorrow and then I can the spray patterns . The vacuum line to the regulator is connected to the smaller of the two barbed fittings at the top of the manifold (not the one bigger one with the little hole in it) . This fitting is clear as I can blow air thru it . The pulse fuel pump was just rebuilt before I bought the motor according to the seller . I opened it up and inspected the diaphragm for tears or shrinkage and saw nothing it looks new . I read somewhere that a hole or tear in the diaphram will allow fuel to leak into the crankcase and cause a poor running rich condition at idle ?
I have a kit for the pulse fuel pump and with the problems I am debating just rebuilding the pulse pump just to eliminate it as a source of the problem .

[EuropeanAM]

Probably a good idea.

[kls2020]

The new pressure regulator I ordered arrived so I put it on and tested it with the same result as the original bypassing at only 10 PSI . The old (original )pressure regulator worked fine with the new aftermarket pump I had installed last month maintaining 36 PSI . I had changed out the original 30 year old pump for reliability . The new pump has a lifetime warranty so I called talked to a tech about the trouble and he sent me another new pump . Opened up the Vst to change pumps and inspected everything looking for blockages . All fitting are clear as I can blow air thru them . I made up a little test set up for the pump /press reg with a tee and 1/4 ball valve I could crack open and throttle to simulate injector flow and the other side of the ball valve I plumbed to the vst fuel inlet for a return line setting up a loop . I took the needle valve and float out of the tank for the testing . I powered up the pump with a 12 volt battery and used a load drop resister to shed 1.5 volts just like the ECU fuel driver when you turn on the key . Ran the newly installed pump with the same result 10PSI and bypassing . I separated the reg from the vst and it was a constant stream of fuel spraying out when the pump was energized . Power down the pump and the flow stops. I was thinking maybe the pump was putting out too much pressure too fast and unseating the regulator valve. I connected the fuel pump to my test gauge alone and when I powered up the pump it came up to 40PSI gradually before I shut it off (10 Seconds?) I was so frustrated I put the original Mercury factory pump back in and it tested everything once again with results the same as before . It has got be faulty pressure regulators I don't see what else would cause this . I am taking both pressure regs to work with me tomorrow and pressurizing them with a precision pressure calibrator so I can determine positively where they are bypassing at even thought I'm pretty sure it will be 10 PSI .

[EuropeanAM]

SIMPLE as pie to determine.

Reassemble, NO FUEL in system yet.

Use a relatively inexpensive AIR PRESSURE gun, pressurize with compressed air and listen to see what pressure the regulator dumps at. Also helpful in checking for leaks (I commonly use this method on "dry" systems beings sent out).

Here's ONE example of a tool to use for this method:

[kls2020]

I have just such a tool at home but used a Fluke pressure calibration set instead . Having the ability to increase air pressure in 0.1 pound increments I was able to verify the new regulator was cracking open at 34 PSI while the original regulator off the motor was opening at 33.8 PSI and both were very consistent . I figured gasoline being thicker that air would require a little more pressure to open the regulator valve .
I am suspecting the ECU fuel pump driver circuit now though I don't think I've ever read anything about a failed ECU making a pump have high pressure output . I am too tired to check it tonight but was wondering if the fuel pump driver uses PWM to control the pump voltage ?

[lpugh]

Because it says Mercury on it, that does not mean it is a Ford with a variable a speed fuel pump...……….134 PSI

[kls2020]

How did I mess that up? Thanks Leon I fixed it

[SilverFox579]

Deleted.

[EuropeanAM]

I have just such a tool at home but used a Fluke pressure calibration set instead . Having the ability to increase air pressure in 0.1 pound increments I was able to verify the new regulator was cracking open at 134 PSI while the original regulator off the motor was opening at 133.8 PSI and both were very consistent . I figured gasoline being thicker that air would require a little more pressure to open the regulator valve .
I am suspecting the ECU fuel pump driver circuit now though I don't think I've ever read anything about a failed ECU making a pump have high pressure output . I am too tired to check it tonight but was wondering if the fuel pump driver uses PWM to control the pump voltage ?

I think you better recheck that with something a little more accurate. No way on earth is that engine gonna run at that kind of pressure!

ASSUMING that the "1" isn't supposed to be there (ie: 034 and 033.8 psi), those would be appropriate and accurate. Regulator should perform within 1 psi with FUEL (as compared to air). This would make me suspect the fuel pressure gauge you are using, also.

Respectfully: Diagnostic attempts are seldom any more accurate than the diagnostic tool information provided.

[kls2020]

Yeah it is definitely 34 and 33.8 pounds I don't know where that extra hundred pounds came from .