D_jet trouble shooting question - car is home, journey continues, June, update- no more problem-- the fix was simple.... |
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D_jet trouble shooting question - car is home, journey continues, June, update- no more problem-- the fix was simple.... |
DRPHIL914 |
Dec 15 2014, 12:39 PM
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#1
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Dr. Phil Group: Members Posts: 5,767 Joined: 9-December 09 From: Bluffton, SC Member No.: 11,106 Region Association: South East States |
OK. car has been in shop for the past week, and today Bob spent several hours on it but what he found was when the MPS is disconnected from the vac hose it will idle and run, but when it gets connected it goes immediately lean and dies, and will not run with that hose on there- the MPS holds Vac no loss of pressure, but that doesnt mean that its not bad.
1- i thought that if an MPS went bad it defaulted rich? but when this is getting vac it goes lean right away and dies. but it will run and idle with out the vac , the AF meter then shows 9.8-10.2 or so which is of course rich but not flooding out. so the question is why is it going lean when hooked up? when this issue started about 2 weeks ago, it had been running just fine and all of a sudden it quit running. 2. could there be another issue we dont see that would be making it way to lean other than the MPS? might need to test another MPS, my 2nd one i just bought from someone here and it has never been opened but will not hold vac (slowly looses vac pressure) so it probably need to be opened and re-sealed. not a good candidate to trouble shoot with. ------ FYI- 1975 d-jet 2.0. newer wiring harness , CHT is newish(replaced 2 months before this issue started and was running perfect at that time) |
Dave_Darling |
Dec 15 2014, 05:59 PM
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#2
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914 Idiot Group: Members Posts: 14,990 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
The MPS plug is bi-directional; flipping it should have no effect.
Something is making the mixture very lean. Unplugging the MPS hose is making the mixture rich enough for the motor to run. Last time I heard of something like this, the fuel pump had failed or very nearly so. There was just enough fuel making it through that the absurdly-large injector pulses from having the MPS unplugged allowed the car to idle, but only just. How's the fuel pressure? --DD |
r_towle |
Dec 15 2014, 09:35 PM
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#3
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Custom Member Group: Members Posts: 24,579 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
The MPS plug is bi-directional; flipping it should have no effect. Something is making the mixture very lean. Unplugging the MPS hose is making the mixture rich enough for the motor to run. Last time I heard of something like this, the fuel pump had failed or very nearly so. There was just enough fuel making it through that the absurdly-large injector pulses from having the MPS unplugged allowed the car to idle, but only just. How's the fuel pressure? --DD Given what is happening, a two minute test might help here. Flip the plug, see if the condition changes. If it does, you need to troubleshoot your wiring harness. |
worn |
Dec 18 2014, 01:21 PM
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#4
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can't remember Group: Members Posts: 3,156 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
The MPS plug is bi-directional; flipping it should have no effect. Something is making the mixture very lean. Unplugging the MPS hose is making the mixture rich enough for the motor to run. Last time I heard of something like this, the fuel pump had failed or very nearly so. There was just enough fuel making it through that the absurdly-large injector pulses from having the MPS unplugged allowed the car to idle, but only just. How's the fuel pressure? --DD Given what is happening, a two minute test might help here. Flip the plug, see if the condition changes. If it does, you need to troubleshoot your wiring harness. Rich, Why flip the plug? The inner prongs go to one coil and outer to the other, so either way you will get the same inductance signal. Which may not be correct as we have heard. Just my $.02 |
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