Engine cranks but will not start

[2Valve]

The wife wanted to go for a moonlight cruise the other night but we were low on gas. I chanced it but ended running out. Got towed in and filled the tank but now it won’t start.

2002 PCM 5.7 engine with 850 hours. Throttle body fuel injection. Engine cranks over fine.

 

I verified fuel pressure up to the throttle body by removing the high pressure line from the FCC and cranking the motor where a strong spray of fuel occurs.

But the twin injectors won’t spray no matter what.

I checked all three engine fuses with an ohmmeter. None are blown. Lastly, I switched off the battery, thinking maybe some error was generated by the ECM. Switched on the battery and still won’t start.

What could have happened?

Thanks, 2valve

 

 

 

 

[S1Pitts]

Engine cover lifted - can you hear the electric fuel pump build pressure and then cut out when turning on the key? It should cycle each time you turn on the key. It might still be vapor locked?

Have you checked the emergency tether switch? they seem to fail at the oddest times. Pull off tether and cycle plunger several times and check to make sure the clip depresses the plunger adequately to activate the switch.

Have you checked for spark on the ignition system? - My spark died when one of two relays mounted on ECM mounting plate failed.

Hope this helps

[Ski_Dad]

have you changed the fuel filter ? - it might have a bunch of junk in it from the bottom of the tank.

[BraceMaker]

Do you have a timing light?

[oldjeep]

Does the fuel line have a bleeder? Could just be air locked.

[2Valve]

@Mitzysman

Yes sir. Changed it in the fall. I even took it out of the FCC to check any differences.

[2Valve]

@BraceMaker

I have a timing light. What are you thinking?

[2Valve]

@oldjeep

There’s a bleeder on the FCC. I bled that for a second while cranking and plenty of fuel exited.

[2Valve]

@S1Pitts

Yes sir. Fuel pressure builds with key on then stops and resumes again while engine is cranking. Tether switch is good. Power to all gauges with key on. I haven’t checked spark.

I’ll check the relays but the timing of just running out of fuel is too weird. The only ‘visual’ issue is no spray from the injectors while cranking the motor.

[2Valve]

I’m going to swap the relays around to see if that resolves it.

[BraceMaker]

Toss it on a wire and make sure you are getting a spark. The spray is usually triggered by the ignition module from a pick up coil on the distributor. No blinkey blinkey and you want to pop the dist cap and disconnect pickup coil and test its resistance. If good suspect ICM.

 

This will give you the visual no spray with a primed system. Injector can be fired by a 9V battery but I would do that off the boat.

[2Valve]

I think I got it. Swapped the two relays and now it runs. The PCM manual says I should have three but I only gots two. I’m guessing one is ignition and one is fuel??

The both are Hella’s, 12193611.

Thanks everyone fir your help. Nothing worse than being my turn to pull the club and boat is down.

 

[2Valve]

Quick update:

After swapping the two relays, of which 3 functions are controlled, (fuel, ignition, starter), everything worked. My thought if it was a bad relay, is something would have failed, like the engine not cranking over.

So I decided to buy new relays anyway and now it won't start again.

My next course of action is to get a timing light and crank the engine to look for spark (timing light strobe) on any cylinder, verifying that the ignition is triggering. I seem to recall that this PCM, the injectors won't spray if the ignition isn't triggering.

[Drago]

Does it fire @ all?

[BraceMaker]

@2Valve correct, if you have a voltmeter with Ohms like you mentioned earlier you can also go right to testing the pick up coil.

 

The fuel injector circuit is triggered by the ICM on the distributor which uses a pick up coil on the distributor shaft under the rotor. This coil is reading pulses from a disc and should have a certain amount of resistance, so if you undo the clip behind the ICM you can use an ohmmeter to read that, and I believe that should be 500-1000 Ohm but certainly not 0 ohms and certainly not an open circuit. Either would say bad pick up. This is a ~10$ part.

 

If that tests good and you don't have spark then you want to check the ICM or you can also check the coil. ICM is about 80-100.

 

If you have a can of carb cleaner you can also see if the boat will fire on a few toots of that which would indicate you have spark and no fuel which would usually eliminate the circuitry of the ignition module.

 

 

[BraceMaker]

And goes w/o saying double check your kill switch lanyard which is a "always do first" thing just like the mower deck on a lawn tractor.

[2Valve]

@Drago

No sir. It just cranks with no hint of firing.

[2Valve]

@BraceMaker

Thanks for the info. Appreciate it.

[eleeski]

A shot of starting fluid addresses things fuel - just to see if the engine will fire.

 

You changed the relays and it worked? Then you changed them again and it didn't? The problem started after fuel exhaustion? Weird problem.

 

With weird problems, disconnect the battery for a couple minutes. This resets everything electrical.

 

Good luck.

 

Eric

[eyepeeler]

I was informed by mechanics to NEVER run your boat out of fuel. The newer electronic fuel pumps are lubricated by the fuel. If you run out of fuel there is a good chance that it could ruin the fuel pump.

 

[Monkstr6100]

Check the actual fuel pressure. If it is low it will not trigger the injectors. More than just depressing the shrader type valve on the rail, put a gauge on it.

[thager]

Check the spade connections on back of safety switch. I had similar event. Engine turned but no fire.

[2Valve]

@eleeski

I swapped the two relays and it worked. Then I changed both for new and it didn't. I re-installed the original relays and it still didn't start. I'm looking at the Ignition Control Module now as a possible source.

[2Valve]

@eyepeeler

Agreed. I attempted to re-start just once and then we got towed.

I DID remove the FCC fuel pump and verified that it was good with some bench testing.

[2Valve]

@Monkstr6100

Will do. I didn't have all my special tools with me but I'll be back out tomorrow night with my gauges. 30psi is what I expect for a TBI system, (what it was producing last fall)

[Gar]

I helped a friend work on one of these if I remember correctly there is a low pressure pump feeding the pump in the FCC. Maybe it's bad don't know.

[2Valve]

@Gar

thanks, but I replaced the low pressure pump last spring. The FCC bowl is filling, so I assume its still good.

[2Valve]

@BraceMaker

I verified that the safety switch is good and working properly.

[BraceMaker]

Good, best luck! I hope its not fuel related, I cannot stand working on the fuel systems of boats.

[Beastmode]

I have had same issue on a 94prostar many times. Fuel pump pressurizing but injectors not firing.

i have unplugged one injector and put a jump wire on injector posts one to ground and the other to a 12v hot(remote starter switch is best)and crank starter and while activating injector and it fires off and starts working. I suspect fuel pump going bad. Causing low prime pressure. Hard to duplicate because it’s random

[Andre]

@2Valve

Here's a VERY good guide to troobleshoothing a no spark/no start on a GM 350.

I have use it on my 94 MC last year and this saturday on a 00 Response lx with same engine as you i beleive.

Real easy to follow.It use another method for checking pick up coil then the Ohms on page 6.

http://easyautodiagnostics.com/gm/4.3L-5.0L-5.7L/distributor-mounted-icm-tests-6

 

Here is what mine looked like last year...

[Edbrazil]

Jody Seal could probably solve the problem in a short time.

 

[vtmecheng]

When it runs out of gas the fuel pump can be damaged. It's possible that the pump was already weak and this made it worse. May want to check the actual pressure. Just a thought.

[2Valve]

@Andre

Thanks very much. I'll be looking at the ICM this evening as the possible culprit.

2Valve

[2Valve]

@vtmecheng

good advice. I thought of that and bench tested the fuel pump with a battery and a fuel hose on the output directed into a gas can. It sounds good and spray is strong.

 

 

[scorban2]

I think it was mentioned, but I'll second testing your rail pressure with a pressure gauge. It's not uncommon for a pump to appear to work well with no head pressure (pumping into a trash can), yet not maintain performance at operating pressure.

[BraceMaker]

@scorban2 that's the value of giving it a shot of either ether (people poo poo on this) or I like carb cleaner right down the bore while its cranking. If it coughs you usually can eliminate the ignition circuit and investigate the fuel system more completely.

 

Trouble with lots of TBI systems is if there is a good place to take the pressure gauge to with out adding a test port as a lot of the TBI non-multiports lack a "fuel rail"

 

In many cases you can slip a T with a test port into the system and leave it there, and this is a very common addition to owners of older LT-1 MC's.

[vtmecheng]

I had a Chevy truck with a TBI engine where the pump died slowly. I got fuel to the injectors but found the pressure was too low once I put a gauge on it. I hated checking the pressure on that truck because I had to install the T @BraceMaker was talking about and always got fuel in the garage or all over my arms.

[2Valve]

I did some more testing last evening, until it got dark and I gave up.

 

Ignition Control module measure 94.5 ohms on the + and C pins. This two conductor harness connects to the coil and the harness ohms out good.

 

The ignition coil (pink wire) and Ignition Control Module (pin +) both have 12vdc with engine on

 

FCC pressure is 30 psi with ignition on, and then falls to zero. When cranking the engine, it rises to 30psi again. I remember this being normal behavior.

 

I totally forgot to write down the pickup coil resistance but I think it was 855 ohms.

 

I should have checked the Ignition Coil switching signal (AC voltage), but ran out of time.

 

I hooked up a timing light to cylinders 1, 2, cranked over the engine, with no strobe present.

 

All connections are clean and tight.

 

I'm down to checking the pickup coil's switching voltage .3 - 1.8vac, and it's resistance again. I hope to do that tomorrow.

 

thanks everyone for your guidance........

 

2Valve

[Andre]

If you end up getting the distributor out for visual of the pick up coil,change it for a new one.It's like,15$.

[BraceMaker]

Sometimes I toss the timing light on the coil wire to make sure it's not a rotor problem.

 

Coil pick up seems OK by that number 500-1500 but it should pulse when rotated. >.25 V AC.

 

 

[Gar]

Make sure you got the correct relay's you installed. There are lots of configurations on those I use to sell them in our auto repair shop.

[vtmecheng]

I also had the pickup coil go bad on that Chevy TBI truck engine. Looked just like the one @Andre posted.

[2Valve]

I'll get back on it this weekend.

thanks

[Dobrodan]

Have you confirmed that the ignition switch is OK? You can have power in the On position and intermittent power in Start if the switch is bad.

[2Valve]

@Dobrodan

Yes, the ignition switch ohms out correctly.

 

I obtained a MEFI Distributor Ignition Manual from a friend of mine. It has theory of operation and test point data that I can use to go through each sub-system, step by step.

 

The toughest part is I'm in the middle of a move. Limited skiing and time for troubleshooting. :(

 

thanks, 2Valve

[2Valve]

the saga gets better....

 

 

Pickup coil test: I expected to see between 500-1500 ohms but instead saw a varying resistance starting at 2.1meg ohms and running up to 2.6megohms. Then it would fall to about 1.7megohms. I have two Fluke meters and verified both gave me identical readings. The changing resistance was acting more like a charged up capacitor than anything else. The pickup coil resistance to ground was infinite as expected.

 

I figured it was a bad pickup coil but decided to check the AC voltage on shaft rotation. That measured good and so I decided to install my brand new Ignition Control Module to see if it would start. And it did. Immediately.

 

Idle was smooth and steady so I decided to go for a ride around the lake, at around 2500rpm, 25mph. The boat felt strong on plane but then started to hesitate and eventually wanted to die, with the RPM's falling. I backed off to idle and it didn't stall, but idle was sort of rough, with the RPM's rising and falling about 300 rpm. I could idle in gear and it would run, but raising RPM's created a near stall condition.

 

Eventually, it would idle smooth again and everything appeared fine, until I tried to plane out again, and the same scenario would repeat the three times I tried it.

 

I got back to my lift, and killed the battery switch for about 30 minutes, thinking it might be a stored error code that I could clear. I then started it again and went out on the lake and the same problem occurred.

 

I should mention that I did remove the distributor but marked the location so I could get the timing close to where it was.

 

If the timing changed slightly, would it cause this condition?

Should I go through the base timing procedure to set the timing more accurately?

Should I maybe pickup a MEFI code scanner to read a possible error code?

Could it be the pickup coil after all, not showing a stable resistance?

 

Thanks,

2Valve

[Andre]

You removed the distributor but didn't replace the pick up coil ? :(

Mine was intermittent too.I coulde ski a couples of sets then no start.

I don't think it's the timing as it started good and ran good for a short while.

Brand new coil is dirt cheap and you'll rule that one out for the rest of troobleshoothing if not the culprit...

 

[2Valve]

@Andre

 

Yeah, in my haste in thinking it was the pickup coil, I removed it but didn't have all my tools with me to disassemble the distributor, so I figured, wth, let's see if it runs with the new ICM.....:)

I think I'll source a pickup coil as suggested.

 

On a good note, I still got to ski yesterday morning and had 2 sets around the lake on pure glass. Problems go away when you're swervin'

 

2Valve

[DW]

@2Valve: FWIW, and not much, but, I interpret you issue to crop up when the boat gets warm or at operating temperature -or- after a few runs or running distance. I would think that makes the issue fall in one of the following:

1. Fuel related due to a weak or low output fuel pressure after some running

2. Heat related messing up one of the electrical components like the coil or the fuel pump

3. Ignition signal being corrupted (which you are troubleshooting) perhaps due to voltage regulator malfunction allowing too much alternator voltage to sensitive ignition components.

 

Just a few guesses, good luck. You pass the nerd test - 2 Fluke meters:)