Hard to start - Now dies returning to idle

[NateCCIE]

I have a 1993 merc 502 MAG EFI (TBI). It doesn't like starting. It seems I have to crank forever, mess around with the throttle and it will finnally catch and run. It doesn't seem to have any problem once it's running. It kind of seems to be getting worse; but yestderday was the first time out since labor day last year.<br /><br />I also noticed that the gasket between the exhaust manifold and elbow is weeping. Hardly any water, but some is coming out. When do you do something about those? Could that be related to the hard start?<br /><br />The boat only has about 425 hrs on it. The PO installed new plugs and wires in I think 2001. I bought the boat last summer.

 

[Bondo]

Re: Hard to start - Now dies returning to idle

I also noticed that the gasket between the exhaust manifold and elbo is weeping. Hardly any water, but some is coming out. When do you do something about those? Could that be related to the hard start?

In Your Case,.......... Before Now .............<br /><br />Ayuh,........ Could Very well Be a Major Player in your Hard to Start Issues.................<br /><br />

The PO installed new plugs and wires in I think 2001.

That boat is Way Over-Due for All of it's Preventive Maintiance,+ a Full,+ Complete Tune-Up............

 

[rabidfish]

Re: Hard to start - Now dies returning to idle

MAP sensor<br />ISCBPA valve<br />Fuel Pressure<br /><br />Verify these and you'll probably have it running again.

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

Bondo,<br /><br />How many hours/seasons should you get out of plugs and wires?<br /><br />Should I do the gasket on the exhaust manifold when I do the ones on the elbow?<br /><br />I would agree about the PM. When I bought it, there was a hole in the shift cable bellows. I just got done replacing all the bellows and hoses on the outdrive and the shift cable. I can only deal with stuff as I find out about it.<br /><br />What would you suggest for a tune-up?<br /><br />Rabidfish,<br />I can't find anything called ISCBPA in the merc manual. What does that stand for?<br /><br />I see in the manual what the map sensor is and what it does, but how do you verify it? What's the best way to verify fuel pressure?

 

[Bondo]

Re: Hard to start - Now dies returning to idle

You got a Manual..???........<br /><br />Look in the 1st couple of chapters.........<br /><br />There Should be a Bunch of Info on Maintenance,.... And a Schedule for that Maintenance.......<br /><br />I Atleast Look at My Plugs every 100hrs........<br />I usually run a compression test while I have them out.......<br /><br />Wires don't get much abuse in a marine application,.... <br />If they Look Bad, Replace them,... I suppose you could ohm check them.........<br /><br /><br />Has this 12 year old boat ever been run in Saltwater,....????<br />If So,..... I'd be buying New Manifolds,+ Elbows/Risers................<br />

I see in the manual what the map sensor is and what it does, but how do you verify it? What's the best way to verify fuel pressure? <br />

That would be done with a Mercruiser Computer..............

 

[Don S]

Re: Hard to start - Now dies returning to idle

Instead of going about this in a hit/miss fashion, since you say you have the manual there, go to page 5C-117 and follow that chart and preform all the tests. Look at your manual, it tells how and where to hook up a fuel pressure gauge, and how to do the tests and what to look for.<br />Even a couple of quick tests right to start with would be to check for spark when cranking. If no spark it won't start.<br />Is there fuel squirting out of the injectors when you are cranking? If not, that may be because there is no spark.<br />Also be sure the battery is fully charged and the connections are all thight and clean. If an EFI engine is cranking slow or showing to low a voltage while cranking, they will not start very easy, if at all.

 

[rabidfish]

Re: Hard to start - Now dies returning to idle

Sorry,<br /><br />ISCBPA = Idle speed control/by pass air<br />Some know it as idle air control valve or "IAC"

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

What does oil on the plugs mean? Blow by? I'm picking up a compression tester tomorrow.<br /><br />-Nate

 

[Don S]

Re: Hard to start - Now dies returning to idle

It means there is a lot of oil getting into the cylinder that shouldn't be.<br />Valve seals, valve guides worn, rings broken, head gasket??????<br />Hard to say for sure, might want to do a leakdown test also.

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

I did a compression test tonight. Here's what I found.<br /><br />Starboard side from bow to stern.<br />90/100/95<br />90/90<br />65/62<br />90/90<br /><br />Port side from bow to stern.<br />90/90<br />60/60/65<br />60/60<br />80/80<br /><br /><br />I put new plugs in before I went to Lake Powell for Memorial Day. It started well the first time, it doesn't like to start after idleing. I ran the motor probably 20 hrs at Powell. None of the plugs look new anymore. Most have oil on them and the middle two on the port side look more burnt than wet oil.<br /><br />When I run on a hose I get white/bluish smoke. I guess this is oil burning.<br /><br /><br />So does all of this mean a rebuild of a motor with less than 500 hrs on it?

 

[newport dave]

Re: Hard to start - Now dies returning to idle

Nate,<br />Mercruiser specs say minimum compression is 100PSI. Definitely time for a engine rebuild.<br /><br />Dave

 

[Don S]

Re: Hard to start - Now dies returning to idle

With compression like that, I would suspect water in the cylinders (Many times) probably from leaky manifold/riser gaskets or bad manifolds or risers.<br />If you rebuild the engine, new manifolds and risers at a minimum would be manditory, or you will see a new engine die within a few weeks.

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

What does it normally run for a 502 mag efi rebuild? 2k-3k or more?<br /><br />What kind on maintanence should be done on the exhaust system to keep this from happening again?

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

Well, so here's my update. After finding out that the 502 isn't a cheap motor to rebuild because of stuff like only JE making pistions for it, I had the mechanic do a leak down test. It showed problems with the valves mostly intake. Had him pull it apart and he said the valve gaskets where not looking too good, and that there were a few valves burnt. He sent out the heads for a rebuild. The cylinders looked good (motor only has 350 hrs on it)<br /><br />It's taken forever but he got the motor back in. Compression is like 135-140 on all cylinders and no more smoke when running on the hose.<br /><br />We replaced plugs, cap, rotor. When he checked it out he thought there was a miss and the timing seemed to be moving all over. He relaced the distributor module I think. I think it was the $100 thing under the coil in the distrubutor...<br /><br /><br />So we took it out to the lake tonight to make sure everything is great. It wasn't. Here's the question part of the post.<br /><br />1. Timing seemed to be jumping all over when looking at the scan tool.<br />2. Engine wouldn't get up to correct WOT RPM. I don't think it went past 4k and I'd expect it to do at least 4500 maybe more (never been on that lake before, but ones close to it.)<br /><br />3.after running at more than an idle pulling the throttle to center the boat died more than once.<br /><br />4.scan tool said everthing is fine, no codes. <br /><br />5. idle rpm was about 700<br /><br /><br />So what could be causing the performance problem and the stalling?

 

[bugup]

Re: Hard to start - Now dies returning to idle

Bondo<br /><br />I was wondering what you meant by the fact it could be a major reason for the starting problem<br /><br /><br />I also noticed that the gasket between the exhaust manifold and elbo is weeping. Hardly any water, but some is coming out. When do you do something about those? Could that be related to the hard start?<br />--------------------------------------------------------------------------------<br /><br />In Your Case,.......... Before Now .............<br /><br />Ayuh,........ Could Very well Be a Major Player in your Hard to Start Issues.................<br /><br /><br />quote:<br /><br />.

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

anyone?

 

[newport dave]

Re: Hard to start - Now dies returning to idle

The timing "jumping around" at idle is normal. The ECM uses timing to control idle speed (in conjunction with the IAC valve). It should be fairly steady at higher RPM under load.<br /><br />Improper timing could account for both your stalling and performance issues. Was the timimg set while in base timing mode? The timing should be very steady and not jumping around in base timing mode. Are you seeing normal IAC activity on your scan tool? What is the IAC position at idle with warm engine?<br /><br />Dave

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

Turned out to be a vacuum leak.<br /><br />I appreacate everyone's input and help.<br /><br />-Nate

 

[waterone1@aol.com]

Re: Hard to start - Now dies returning to idle

Nate, glad to hear she is running good. Did you have the exhaust manifolds and risers inspected while they were off ?

 

[NateCCIE]

Re: Hard to start - Now dies returning to idle

I did have them inspected. All it needed was new gaskets. Fresh Water use doesn't hurt them very much at all.<br /><br />-Nate