still at it....help please

[paulc229]

got it "running" after partial submersion, replaced shorted starter, replaced high pressure fuel pump inside vst, vst is getting fuel, will run for about 5 sec at low rpm, then die. could it be fuel pressure regulator, seeing as im getting 0psi at shraeder valve, even though i know there is some pressure when i take off the gauge it spits a little fuel out? Is there a way to test the regulator(other than at the shraeder valve)

 

[Tim75]

2 reasons I can think of for 0 psi:

1) electric vst pump is wired backward. It will run, but no pressure.

2) stuck inlet float needle in the top half of vst tank. It can be stuck anywhere between closed and full open.

Schrader valve is the only place to check pressure.

Have you checked the lift pump and pulse pump for delivery?

 

[paulc229]

I’ll check the float needle, on my pump the positive post is smaller than the negative post and probed with multimeter shows +current, can hear the pump that clicks(thumps), and the electric pump, I thought that since the vst is filling the other two must be working?

 

[Shortrun]

Just question i thought of.
if one or more injectors are leaking it may effect the pressure. You should be able to see this if you check the spark plugs. some would be really wet.
I was wondering about the pressure regulator.

Are people just using a tire pressure gauge to check pressure at the Schrader valve?

 

[paulc229]

I was thinking it was something that was caused by the partial submersion since it ran great before that

 

[paulc229]

So I decided to do a spark test, no spark on the bottom two cylinders port side, and the bottom cylinder starboard side…… checked trigger and they are all around 1275 ohms

 

[ripcuda]

Spark for cylinders #4,#5,#6 all share the same stator charging coils (Wht/Grn wire).
Test the stator charging coils:

Also from service manual:
"CDM #4, #5 and #6 get their charging ground path through CDM #1, #2 or #3
A shorted Stop Diode in CDM #1, #2 or #3 would prevent CDMs #4, #5 and #6 from sparking."
-- So pull the CDMs and do the diode & resistance tests on them.

Cheers!

 

[paulc229]

thanks rip, 411 on the stator, and 0 on the other two to ground, going to look up in the manual how to do the cdm tests.

 

[paulc229]

ok so checked the cdm resistance tests, did the diode ones just on ohm setting as i dont have a diode setting on my multimeter, not sure if that actually means anything, all six are the same within a few ohms, the averages for the 6 tests are as follows. test 1 stop diode forward bias = OL(should be continuity), stop diode reverse bias .498(should be no continuity), return ground reverse bias .391(should be no continuity), return ground forward bias OL(shoudl be continuity), trigger input resistance 1235( 1000-1250), coil secondary impedence 1062(900-1200). What does this tell me if anyting....lol

 

[paulc229]

Tried resting the switch boxes, was looking for the white/blk bullet connection, and this is the only one I could find white/blk on one side, and brown coming from box? Is this the one to ohm

 

[Tim75]

ok so checked the cdm resistance tests, did the diode ones just on ohm setting as i dont have a diode setting on my multimeter, not sure if that actually means anything, all six are the same within a few ohms, the averages for the 6 tests are as follows. test 1 stop diode forward bias = OL(should be continuity), stop diode reverse bias .498(should be no continuity), return ground reverse bias .391(should be no continuity), return ground forward bias OL(shoudl be continuity), trigger input resistance 1235( 1000-1250), coil secondary impedence 1062(900-1200). What does this tell me if anyting....lol

If I remember Multimeter 101, your readings are good. It seems that you had the test lead polarity reversed.

OL is Over Limit. Exceeding the max reading for that scale. Could be read as infinite resistance.

.498Ω -- Depending on your range setting. On the lowest Ω range, that is almost perfect continuity. Does your meter have a "beep" continuity function? Repeat the test on that scale. Does it beep?

Your other tests seem OK. However, I have had parts test good, but fail when they get hot.

 

[Tim75]

If I remember Multimeter 101, your readings are good. It seems that you had the test lead polarity reversed.

OL is Over Limit. Exceeding the max reading for that scale. Could be read as infinite resistance.

.498Ω -- Depending on your range setting. On the lowest Ω range, that is almost perfect continuity. Does your meter have a "beep" continuity function? Repeat the test on that scale. Does it beep?

Your other tests seem OK. However, I have had parts test good, but fail when they get hot.

Not sure about the tan wire, but the black w/ yellow stripe is the engine kill wire. You can disconnect and try running.

 

[paulc229]

Thanks Tim, the only multimeter I have only does autorange, so I can’t change the range. I looked it up, and it does like the cdm are testing fine and since it doesn’t run long enough to get hot, don’t think they are the problem. Next item on the list is the switch boxes, top is supposed to be the ignition control, and bottom is rev limiter but the manual says to ohm the white/blk wire and that’s the only white/blk wire coming from switch boxes. This is a remanufactured engine so they might have used different color wire?

 

[paulc229]

Well not sure what the heck just happened, removed all cdms to test, put them all back on in original spot, removed vst to confirm float needle working replaced. Tested spark again, and spark to all 6, tested fuel pressure at shrader 36psi, all seems to be good. I did notice when I removed cdm for #5 cylinder there was some water inside the wiring harness, so maybe just had to fry out? But none the less, back to 1000 rpm idle didn’t go crazy but up to 5000 rpm and all good. Thanks for all your help!