Crank no start....no spark/injector pulse

Bliss36 · **Posted:** Sun Apr 15, 2012 10:02 pm

I have a crank/no start condition that's driving me nuts right now on our 268 Vista W/ Volvo 5.7 GI-E. Any input is appreciated!
Here's what I have tested so far:
Fuses/breakers-ok
Crank sensor-B+,ground, and signal output=ok(also tried new sensor to be sure)
Camshaft-B+,ground, and Signal output =ok
Ecm -grounds=ok
Coil/ignition module=ok when I supply signal input to ignition module the coil fires
Engine grounds=ok(continuity/low resistance to battery ground)
It seems the MEFI-4 ECU is receiving the signal from sensors but is not putting out a reference signal for injector pulse or ignition. From everything I've tested it seems like a bad ECU, but from what I've read the Delphi MEFI-4 Ecu is near bulletproof. Any idea's? Am I missing something obvious? Also does any one have a color coded wiring diagram for this engine? Thanks!

230 Mike · **Posted:** Mon Apr 16, 2012 12:46 am

Safety lanyard?

aguyindallas · **Posted:** Mon Apr 16, 2012 6:40 am

When I ran a new VHF antenna wire, I accidentally pulled off a wire from my ignition switch. Have you check those connections?

firecadet613 · **Posted:** Mon Apr 16, 2012 7:03 am

If I remember right, he's got it cranking, but no spark.

Already checked the neutral safety switch, and the safety lanyard which was my guess.

I've got no idea, but I was hoping to see a text from you saying you had got it. I've got a scanned copy of that schematic in your email in color...

Bliss36 · **Posted:** Mon Apr 16, 2012 8:03 am

firecadet613 wrote:

If I remember right, he's got it cranking, but no spark.

Already checked the neutral safety switch, and the safety lanyard which was my guess.

I've got no idea, but I was hoping to see a text from you saying you had got it. I've got a scanned copy of that schematic in your email in color...

Yeah this thing will crank all day but no spark/inj pulse. The new wiring diagram should really help..Thanks!! I'm just not feeling comfortable condeming an $800.00+ computer without being 100% sure that's what it is. This problem started last fall when i was winterizing it just died out while running and wouldn't restart.

aguyindallas · **Posted:** Mon Apr 16, 2012 8:26 am

When I knocked my wire loose, the engine would crank too...just wouldnt fire.

Bliss36 · **Posted:** Mon Apr 16, 2012 8:29 am

aguyindallas wrote:

When I knocked my wire loose, the engine would crank too...just wouldnt fire.

That's good to know! I looked at my ignition switch wires thru my cup holder cutout yesterday and they were all attached but I'm wondering if it could also be a partially failed ignition switch....that would be great(cheap)!Thanks I'll check that!

Graham R · **Posted:** Mon Apr 16, 2012 9:54 am

Or maybe it's that multi pin connector behind the dash that connects the dash/ switch panel wiring to the main loom; mine was loose a few years ago and caused all sorts of weird problems (including the engine refusing to stop, even when the kill cord was removed, the only way I could stop it was to remove the connector to the distributor! I never figured out where the engine was getting a +12V supply from but thankfully it's never done it again ! ).

There's also the multi pin connector by the circuit breaker on the engine that can come loose.

Plus the ignition relay in the electrical box on top of the engine. That's the one between the 15A F3 fuse (ignition / fuel) and the 15A F4 fuse (ECM). There is (or would have been originally) a spare relay in that box (alongside the row of 6 spare fuses). You can download a owners manual from the VP website, there's a drawing of that box on page 45.

ric · **Posted:** Mon Apr 16, 2012 10:23 am

If the ECU is powering up, the ignition switch is working. If it's cranking, the safety switch is working (and the neutral lock out).

The MEFI4 setup is about as basic as fuel injection goes. When the engine cranks over, do you see it outputting an RPM signal?

Bliss36 · **Posted:** Mon Apr 16, 2012 10:28 am

ric wrote:

If the ECU is powering up, the ignition switch is working. If it's cranking, the safety switch is working (and the neutral lock out).

The MEFI4 setup is about as basic as fuel injection goes. When the engine cranks over, do you see it outputting an RPM signal?

Yes the Tach does show cranking rpm. I did see it bounce around wildly a couple times but then settle down

ric · **Posted:** Mon Apr 16, 2012 11:01 am

Bliss36 wrote:

ric wrote:

If the ECU is powering up, the ignition switch is working. If it's cranking, the safety switch is working (and the neutral lock out).

The MEFI4 setup is about as basic as fuel injection goes. When the engine cranks over, do you see it outputting an RPM signal?

Yes the Tach does show cranking rpm. I did see it bounce around wildly a couple times but then settle down

There's nothing about the signal that should bounce wildly. I'm not well versed on the MEFI setup but 99.9999% of all EFI setups use the crank sensor for ignition signal. If the magnetic sensor is reading wildly at times it will output signal higher or lower then the program's known variables and signal a fault. A fault on a crank sensor is an instant no start situation and not fire anything. I would check the part numbers for that sensor, it's a generic GM crank sensor that you can pick up at the auto parts store for cheap.

The cam sensor is 99.999% only responsible for the injector firing but used as an RPM reference sometimes. Again, I'm not 100% knowledgeable with GM's MEFI4, but generally when that sensor fails only the injectors quit firing, it generally might still spark.

Bliss36 · **Posted:** Mon Apr 16, 2012 12:27 pm

I replaced the crank sensor yesterday because I thought it was suspect, but no change. I recorded a signal output at the sensor and traced it to connector J2 on the ECU, where it also showed signal from the crank sensor.

It just seems like the sensor info is going into the ECU but it's not sending out a signal to the injectors and distributor.

ric · **Posted:** Mon Apr 16, 2012 12:51 pm

The easiest thing to do would be to borrow another ECU for testing, if you can find one. Or a scan tool/pc software.

I have a Lexus and they're pretty famous for the ECU's messing up with my engine package. They overheat and the ECU pops capacitors causing ALL sorts of weird issues saying all sorts of sensors are bad when they're not. Anywhere from not running, not shifting into overdrive, or literally dumping fuel and you can light the exhaust on fire. I'd pull the cover and see if anything looks funny.

Bliss36 · **Posted:** Tue May 01, 2012 10:56 pm

After a couple of very frustrating weeks I'm happy to report our boat is fixed!! After much testing I decided the ECU was the culprit and order one up. Once ordered I decided to open up the back side of the damaged one to take a peek inside and what I saw helped to confirm my diagnosis.

The potting jelly was blown out in the area that the crank sensor signal,power, and ground came in. I received my new ecu monday, plugged it in and it still didn't start but my engine alarm was sounding...this was new. Tonight I traced the Crank sensor harness from start to finish and found where the wires passed in between the knock sensor/block drain they were crushed against the block by the body of the knock sensor. Looking at the harness you couldn't tell anything was wrong until I pinched the wires between my fingers, then I could feel a weird kink in the harness. I must have ran resistance and continuity checks on the harness a dozen times and still missed this

*Harness unwrapped and showing previous routing*

*Pinched wires*

2 out of the 3 wires were damaged and rubbing against the block including the ECU supplied power the the crank sensor. I assume a power supply short to ground is what smoked my ECU. It really sucks that I spent so much time and money, but honestly right now I'm so happy our boat is fixed that I'm not thinking about that! We're ready to get this season started!!

jsimon · **Posted:** Wed May 02, 2012 6:14 am

Ben

First, great troubleshooting! Wondering though could you have burned up the new ecu with the pinched wires before you found them?? That would have really sucked.

Or is there any chance it could have damaged it it any way?

The good news about the whole thing is it didn't happen on your trip last year or your upcoming one!!

www.iFourWinns.com

Crank no start....no spark/injector pulse

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