What are the chances my MIL is burnt out?
- Thread starter Greg Corcoran
- Start date
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Greg Corcoran
SHO Member
my electrical and vacuum Helm manual came today and poking around in it I think I figured out my unused connector at the firewall by the intake. Obviously now I know it's not the EGR connector. I am apparently missing my cold engine lock out switch, something in the climate control that goes in (or on) the heater hose? Prior owner had the heater core replaced, and the heater hoses at the same time, so that switch must have been a casualty. I'm guessing that's not a highly important switch?
Cycling the ignition 3 times prior to starting to overcome a possible bad fuel check valve didn't pan out. Had another hard start this evening after work. Prior to tonight I had no hard starts in the last two days while doing the three ignition cycles to run the fuel pump, so I was getting hopeful that I had an answer, but now it seems not. Is there also a check valve in the fuel rail pressure regulator( return line to the tank)?
Cycling the ignition 3 times prior to starting to overcome a possible bad fuel check valve didn't pan out. Had another hard start this evening after work. Prior to tonight I had no hard starts in the last two days while doing the three ignition cycles to run the fuel pump, so I was getting hopeful that I had an answer, but now it seems not. Is there also a check valve in the fuel rail pressure regulator( return line to the tank)?
Have you set a gauge on the fuel rail to quantify the pressure?
What was the outcome of the disconnecting the CPS sensor
Greg Corcoran
SHO Member
Sorry for the late reply - I was away for the weekend. I didn't want to confound the fuel pump check valve test with the CPS testing since a long cranking time could be either. Now that I'm confident it's not the check valve I'm going to unplug the CPS.
I thought I had a fuel pressure gauge with a Schroeder fitting that went to 60 psig, but all I can find is my dad's old gauge that is set for carburetor fuel pump pressures (<10 psig). So - no, I have not checked pressure at the fuel rail yet. I'm going to go buy a gauge. My understanding is I'm looking for 46 - 49 psig?
luigisho
SHO Member
You might even be able to do the loaner tool for this at one of the box stores
I got mine from Autozone. I know it reads at least 80 psi since one of my cars had a faulty fuel pressure regulator. Normal pressures are around 40 psi or less.
Greg Corcoran
SHO Member
Car won't run with cam sensor disconnected.
First time it started up, ran a barely a second then slowly died off in another second. 9 or 10 more attempts would not start and I could smell gas. Plugged sensor back in and had to floor the pedal to clear it out and get it to start.
Second attempt was this morning - no start after 10 attempts, gas smell again. Sensor reconnected and held gas pedal all the way down until it started.
So I thought SHO was supposed to run w/o cam sensor it just needed to try up to three times to get the injectors synced with the spark? The sensor has apparently been replaced once before - the locking tabs are broken off the connector and there was silicon grease in the connection.
Also - I bought a fuel pressure gauge and Ford EFI adapter. Running I have 36 psig. I thought I was supposed to have 46 to 49?
If I unplug the return regulator vacuum line it drifts up to 40 - 42, not always same reading each time I unplug. Once vacuum line connected to regulator it goes right back to 36 every time. If I cycle the key on several times without starting engine the pressure will go as high as 46 briefly then drop to either 36, or 0, or something in between, as soon as I release the key. Seemingly random residual fuel pressure reading...
I'm drawing three possible conclusions -
1) Bad fuel injector(s) sticking sporadically, leaking down causing loss of fuel pressure when shut off and squirting waayyy too much at startup when cam sensor unplugged flooding out and causing no start when PCM is trying to align ignition and injectors. This would account for my occasional hard starts: too much fuel and/or not enough pressure. Possibly fuel delivery imbalance causing the violent surging at 3000 rpm when cold?
2) Bad check valve/weak fuel pump. Valve sticking sometimes, not others, pump cannot put out 46 psig like I think it should. My surging when cold at 3000 - 3500 rpm is fuel starvation from low pressure, my hard starts are lack of residual fuel pressure. This theory does not account for the no start when cam sensor unplugged. Not sure it accounts for the surging going away as the car warms up.
3) Something else is ***** in the ignition module, coil pack, or PCM so it can't adapt to the cam sensor being unplugged and figure out how to run the engine. Whatever the odd failure mode is causes my violent surging at 3000 rpm when cold. Whatever this odd failure mode is it is temperature dependent and self heals as the car warms up. Fuel check valve is also messed up(see door number 1).
I'm leaning towards door #1 since it accounts for my symptoms AND the behavior when the CID is unplugged. Door number 3 seems like a stretch as it is two problems, one of which seems like magic. Door number 2 seems possible, but the cam sensor unplugged no start seems to argue against it.
Whaddya think?
Greg Corcoran
SHO Member
Wait, CPS is crank position sensor not cam sensor? I did not unplug that. My understanding is SHO can't run without a valid CPS signal.
CPS = Camshaft Position Sensor
CKS = CranKshaft position Sensor
CKS = CranKshaft position Sensor
So is your CCRM working or did the second one you bought get damaged
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well, when the cam sensor is unplugged, the pcm guesses which cylinder is number one, and you have to keep trying until it guesses right. while it typically only takes 3-4 tries for it to guess right once (odds are 1/3) it is certainly possible that it could take 10 times or more without guessing right. all during those tries, it is squirting fuel into the cylinders so it would be reasonable to be flooded after 10 failed attempts. so your statement that "it won't run with cam sensor unplugged" is incorrect and you had a bit of bad luck. hope you didn't buy any lottery tickets lately...
your fuel pressure randomly dropping to zero when cranking stops is going to be either door #1 or #2. test for the pump check valve by cycling the key switch to on for 2-3 seconds, several times to see if it builds up pressure.
your fuel pressure randomly dropping to zero when cranking stops is going to be either door #1 or #2. test for the pump check valve by cycling the key switch to on for 2-3 seconds, several times to see if it builds up pressure.
Greg Corcoran
SHO Member
Tried w/o cam sensor again tonight with gas pedal held ~1/2 way down to counter flooding. No
Joy after 4 really long attempts. Battery was apparently fading so I stopped. I'm guessing my PCM can't guess. Ever.
Or there is some obscure secondary failure that combined with no CID signal prevents ignition?
Yes three successive key ons has fuel pressure increase each time until 3rd time when it peaks at about 46 and retreats to 40 and holds. Must be a relief valve in the system. I left the gauge on at 40 pasig showing overnight. I'll see if it drops much overnight.
Ordered a fuel pump assembly from NAPA. None in western US. This one is coming from IN. Should have it Thursday or Friday I hope.
I will call around and see who can "motovac" my injectors this week to rule that out.
Joy after 4 really long attempts. Battery was apparently fading so I stopped. I'm guessing my PCM can't guess. Ever.
Or there is some obscure secondary failure that combined with no CID signal prevents ignition?
Yes three successive key ons has fuel pressure increase each time until 3rd time when it peaks at about 46 and retreats to 40 and holds. Must be a relief valve in the system. I left the gauge on at 40 pasig showing overnight. I'll see if it drops much overnight.
Ordered a fuel pump assembly from NAPA. None in western US. This one is coming from IN. Should have it Thursday or Friday I hope.
I will call around and see who can "motovac" my injectors this week to rule that out.
Greg Corcoran
SHO Member
Well, new one is mostly working. The low speed fan relay crapped out in about a week. This new one was an NOS CCRM. Turns out my low speed fan windings had incredibly low resistance, so must have been pulling all kinds of amps. Damaged the contacts by arcing I imagine. Got a new radiator cooling fan put in, and now waiting for my original CCRM to get serviced and returned. I'm having the guy replace both Bosch 50A relays for the fans.
Greg, I don't think you're quite getting how this works when the cam sensor is unplugged. When you turn the key to start, with a total lack of cam sensor input, the pcm guesses which cylinder is number one and fires the coils according to that guess. This guess is locked in as long as the key is "start" or "on" so a "really long cranking attempt" will only result in flooding and wearing down the battery. The pcm will guess again the next time that the key is turned to start. Therefore, the trick to making this work is SHORT cranking attempts, only long enough to get the engine to start if the spark is going to the right place at the right time.
sperold
Last to Know
^^^^^^ This.
What helps me make sense of this is the fact that with the SHO, 2 plugs fire at the same time (called sacrificial spark or some such term). With a 6 Cylinder, the pcm's hunt for #1 cylinder is not 1 in 6, but 2 in 6 (1 in 3) because the system still works even if the sacrificial plug firing is mistaken for the real #1.
Every car has a favourite time duration to fire-up. Once you have rolled over the engine past this time, you are wasting your efforts; if the system guessed wrong, no amount of cranking will encourage it to start, as it is basically out of time.
What helps me make sense of this is the fact that with the SHO, 2 plugs fire at the same time (called sacrificial spark or some such term). With a 6 Cylinder, the pcm's hunt for #1 cylinder is not 1 in 6, but 2 in 6 (1 in 3) because the system still works even if the sacrificial plug firing is mistaken for the real #1.
Every car has a favourite time duration to fire-up. Once you have rolled over the engine past this time, you are wasting your efforts; if the system guessed wrong, no amount of cranking will encourage it to start, as it is basically out of time.
Greg Corcoran
SHO Member
OK - one more try. 4 times just as long as the 'average' start time. (I had been holding key for at least as long as the 'longest' time to start when it's misbehaving). On that fourth try it sounded like maybe it sorta stumbled a little but didn't start. So I held the pedal all the way down and tried a few more times. On try 7 (3rd with the pedal floored) it started! Ran like crap for a few seconds then cleared out and idled properly. Flooded right? And of course the tach was dead and check engine light was on. Fuel Pressure was 36 when I started this test and went as high as 46 just like before. running it was 40.
Took it for a test ride. No change. I'm presuming the bucking was around 3000 rpm since I had no tach.
So - all indications point to...?
I'm thinking one or more injectors is having issues. OR - the return pressure regulator is sticking? the big question - why does it self heal as the car warms up? I'm open to other suggestions that can explain this logically.
ok so it sounds like you have ruled out the cam sensor as being part of your issue.
fuel pressure appears to be in the range (running fuel pressure will vary with intake vacuum, less vacuum = higher fuel pressure).
I would be looking at injectors next - clean or replace.
fuel pressure appears to be in the range (running fuel pressure will vary with intake vacuum, less vacuum = higher fuel pressure).
I would be looking at injectors next - clean or replace.
Greg Corcoran
SHO Member
While the injectors are 22years old the car only has 80K. It's been doing this since I bought it with 76K last spring. Prior owner said it had just started (for what that's worth). I'm going to call around and look for a shop with a motovac tomorrow since I hope the injectors are not worn out, but gummy from lack of use over last 22 years.
Is the fuel pressure regulator replaceable, that's all that will be left? I hope it's something still available. Also, just went out and looked at the pressure gauge. It's 7. Was 36 last time I looked a couple hours ago, it was 38 when I turned off the car after the test drive. Fuel is going out someplace. Pump Check valve, regulator, or drippy injectors. Think we've ruled out the check valve. I'll address the injectors this week.
I found the box with the factory injectors from my 92 SHO. They've been sitting on the shelf since about 2001. Probably had 120K - 130K miles on them when pulled. Anyplace to get them refurbished and flow matched?
Fuel pressure regulators can still be found. I've used the ones from Napa (Echlin), but Shosource now carries them. It can be replaced with the intake on, but it is a bit tough to get a wrench in there. It's easier if you pull the intake. However, based on your numbers, I don't think you need a new FPS.
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