Random Hard start, suspecting electrical or ignition

I have a 1993 Mercruiser 3.0L that I've been fighting for off an on for a while involving a hard start and at idle sometime dies systematically.

Info update:

Fuel pump failed: Replaced in April

Ran rough at idle all the time and was difficult to start: Carb rebuilt.

When it would idle, it would idle normal. However very difficult to start warm: Service shop lake tested, the adjusted float level for free to resolve it.



Now:

Idles better and dies less often but the hard starting still appears at random intervals and I hear sprattic random popping through carb at times. Generally occurs most when slight throttle from starting to running transition, OR when I shove the throttle down for a fast WOT start.

Also, now I believe most of the issues where it dies ends up shortly after a hard start.

Also, the float adjustment seems to have made my hole shot a bit longer too.


Notes Found on lake test:

I've noticed when I have the hard start issues. A time or two I seen the voltage drop to 12 volts or about 10.5 after the engine caught up and was at idle speed. I don't remember seeing this consistently, but it was there. I would notice the voltage would drop before the RPM's would drop to about 10 volts. Then it would stumble and gave it 1500 rpm's of gas, but it would hover near 12 volts or less then.

Tachometer at times would report correctly, other times it would be completely wrong. I've heard this can possible end up being a coil issue.

The ignition coil was normal temperature. However, the altenator was a little bit more warm than expected. It was not too far from the temperature of the engine block. No noise and most of the time I remember seeing near 13 volts most of the time on the dash guage.


I have the service manual, but could someone repeat the testing criteria for the ignition coil module to see if it is defective?

I believe carb/fuel related has been investigated to its death and ignition needs to be verified. I have some very hard to find gremlins that are well disguised, and its getting to be a real pain.

Re: Random Hard start, suspecting electrical or ignition

Cold ignition coil tests out 100% on all service manual procedures. Had to buy some 12v wire clips to get a reading. As my first method used didn't work about 1 month ago.

Going to do another lake test and see how it reports after it gets warmed up with use.

I'm going to get to the bottom of this crappy random hard start and random dieing issue.

Re: Random Hard start, suspecting electrical or ignition

I have some very hard to find gremlins that are well disguised, and its getting to be a real pain.

Click to expand...

Ayuh,.... Sounds like the carb has been fiddled with, but not Rebuilt, nor replaced....

'n it sounds like a fuel delivery issue to Me....

Re: Random Hard start, suspecting electrical or ignition

havoc_squad said:

Notes Found on lake test:

I've noticed when I have the hard start issues. A time or two I seen the voltage drop to 12 volts or about 10.5 after the engine caught up and was at idle speed. I don't remember seeing this consistently, but it was there. I would notice the voltage would drop before the RPM's would drop to about 10 volts. Then it would stumble and gave it 1500 rpm's of gas, but it would hover near 12 volts or less then.

That's some pretty important info there. You should not be seeing voltage that low while running. Nothing less than 13 even. 13 -14 volts or so shows a working alternator.

An engine is not going to be happy running at 10 or 11 volts.

Confirm the volts gauge is correct and keep an eye on it, There may be a sporadic issue with the alt. and/or wiring to it, causing this ^^^

Click to expand...

Re: Random Hard start, suspecting electrical or ignition

Long story short, my service shop is now "FORMER" service shop.

The whole bloody issue boiled down to the wrong fuel pump gasket installed by service shop, causing a flooding issue due to the wrong fuel pump arm clearance.

I figured this out myself with some help from another shop's Master Merc Tech at the parts department. Sold me a thicker gasket, I installed and tested with pressure gauge, flooding problem solved...

For a service shop that works on tons of competition grade Wakeboard boats and sterndrive boat customers, this was unacceptably bad diagnostic service for 3 trips for it to be serviced and $500 of wasted money. (Not including fuel pump cost, old fuel pump was bad).

I have taken my business elsewhere and will not put up with persistent incompetence. I can understand mistakes and the nature of the business, but these incidents destroy trust that customers put in their service shops.

Re: Random Hard start, suspecting electrical or ignition

havoc_squad said:

The whole bloody issue boiled down to the wrong fuel pump gasket installed by service shop, causing a flooding issue due to the wrong fuel pump arm clearance.

Click to expand...

Glad you got it fixed.... but that is something I've never heard of. Frankly, I find it hard to believe that is your problem. Check back in and let us know if this is your permanent solution.

Re: Random Hard start, suspecting electrical or ignition

It's a confirmed issue that most of the Master Mercruiser techs worth their salt know about quite well.

The IL4's require a thicker cork based gasket to provide the proper clearance distance for the fuel pump rocker arm. The wrong gasket was installed on it, they put the gasket that was meant for a V6 or V8 engine.

I figure my former service shop ordered a fuel pump kit with the wrong gasket that shipped with the pump. No one bothered to reference the online parts manual, and NO one bothered to do a pressure test after installing.

I could have lived with that if they would have caught this after doing a carb rebuild. Unfortunately they didn't, and what was worse they "attempted" to fix the flooding issue by screwing up my float settings after I complained that it flooded badly.

It ran terrible after that, and I reset the float settings BACK to Mercruiser service manual specs.

Then I broke down and bought a fuel pressure test fitting with a tester gauge.

PRESTO! Instant answer, fuel pump was overpressurizing.

From there it was diagnosing the fuel pump issue.

Yes, it was a platinum Mercury service shop and their service manager who must be a Master Merc tech. He saved me $160 plus tax with just a $3 quicksilver gasket that was needed.

I figure they ordered an aftermarket marine fuel pump and got shipped with this gasket at the picture below:



See the thin blue gasket, that's what I found on my engine block when I uninstalled my fuel pump and scraped off. It's about the thickness of construction paper.

The correct gasket that is shown below is: 43186 1



It's about almost an 1/8 of an inch thick of cork gasket. That 1/8 of an inch is the difference between +20 PSI and 5 PSI stable for the fuel pump.

I am a living example of this issue does exist in real life. People are not careful on what gasket they order with mechanical fuel pump on the mid/late 1980's to mid 1990's GM IL4 block engines and get flooding issues after a fuel pump install.