S52 OBD1 cranks but won't start

[hammslice]

I wrestled in my mind a bunch hooking them up between all the twists in the pipes and looking from the top and the bottom and the front and the back.

These pictures that I just took show that the bottom line from the previous post crosses and runs inboard on the car and then goes to the fuel filter. The outboard line goes directly into the tank.

[325islovE]

fuel flows in from the front of the fuel rail to the rear where the regulator is located. what is connected? tps, maf, dme power/ground, o2 sensor... is your maf in the right direction

[hammslice]

Yeah I have the feed line going to the front of the motor.

Everything is connected and I'm pretty sure the MAF is the right way. It has an arrow on it.

If my fuel pump relay is good, what would cause it to only run when jumped?

[samiam3356]

Mike and them had a car that wouldn't crank because there was some left over wiring from a car alarm. Just throwing it out there

[hammslice]

Thanks for the suggestion. There is a box hanging down below my steering column that I don't know what it is. If the car had an alarm the PO didn't tell me about it/know about it, but he wasn't the first owner.

I've also been reading mixed messages on grounding the case of the ECU. I guess its also worth a try.

[samiam3356]

The ground on the shock tower is the ground for the DME.

[hammslice]

After browsing RealOEM.com, I think that box hanging down is just the gong.

[MattM]

the box could also be the OBC computer thingy..

[hoveringuy]

I am using the M44 crank sensor (12-14-1-247-62) in the stock S52 location per the advice I got in the only other question I asked. http://www.r3vlimited.com/board/showthread.php?t=185778 This is the only sensor I bought new so it should be good.


Any help is very appreciated. TIA.

I'm using that sensor and it's been fine, although I had to cut the plug off and splice directly because of my extra connections to the VANOS control board.

It's critical that the crank signal is on the yellow wire. Since you probably still have the plug it should be Ok, but I never verified that the M44 plug is pin compatible with M50 harness. With the wrong polarity it just won't start, even though it's an AC signal. Go figure.

The ECU will only trigger the fuel pump once it receives a signal from the crank. My pump will prime when I first turn the key occasionally, but not always.

[hammslice]

Since you probably still have the plug it should be Ok, but I never verified that the M44 plug is pin compatible with M50 sensor.

Thanks, I'll try to check into this tonight and report back.

Update: I will have to check this out IRL, but it looks like you might be on to something. "US production only" aggravates me!

[hammslice]

i checked the pins on the harness and 1 yellow goes to 16 at the DME, 2 black goes to 43 at the DME, 3 goes to ground.

on the sensor i get a resistance of 570 ohms over 1 and 2. i think it should work to just plug it into the harness as is. is there a way I can check the polarity without cutting the sensor to look at the colors?

is there anything i can do to trick the DME at this point just to see if its the issue? obviously said trick would not allow me to start the motor, but it might get me one step closer.

[hoveringuy]

It looks like your M44 plug only goes to connector X6203 which is identical to that on the M50: Pin 1, yellow. Pin 2, black. Pin 3, gnd.

Just make sure yellow goes to yellow.

I have no idea what connector X6091 is. U.S. M44s have 2 connectors between the CPS and ECU?? WTF?


Edit: with the sealed cable on the M44 sensor the only way to tell for sure is to 'Scope it and look for the proper waveform.

[hammslice]

Sadly, i don't have access to an oscilloscope. I feel like based on the diagrams it must be correct. The symptoms seem to point to the fact that the DME isn't getting a signal from the crank sensor tho.

What other signals does the DME rely on before it will power the fuel pump and so on?

Also, as another follow up, i verified the case of the DME has good ground through the harness.

[hoveringuy]

[quote=hammslice;2449023
What other signals does the DME rely on before it will power the fuel pump and so on?
[/quote]

When I was devoping the Hall to VR converter I had my motor on a stand and a crank signal wheel on a bench grinder with a VR sender.

All it took to get the sparkplugs snapping, injectors clicking and fuel pump relay energized was to spin the wheel.

I swear that my lasting contribution to mankind will be to make a simple 60-2 wheel emulator with the proper connector to troubleshoot DOHC.

I was also testing the smaller VR sensor as a possible solution but it didn't put out enough voltage at cranking rpms to be reliable.

[hammslice]

so what I should do? start looking for an OBD1 toothed pulley and ditch the underdrive pulley that is on there?

I love a good challenge, but I'm ready to admit that I can not figure this one out. I just don't know where else to look. The M44 sensor seems to be the only that I did differently that the majority.

EDIT: or I could try your hall to VR converter with the stock s52 crank sensor?