1998 7.4 L MPI intermittent starting problem

[koresample]

My '98 270 DA with a single 7.4 L MPI (879 hrs) has had an intermittent starting problem that i am trying to determine how best to troubleshoot. I just got it two months ago and have done a ton of work to it (new manifiolds/risers/water pump/batteries/cables-end/new hydraulic steering plus a ton of new electronics and cosmetic updates). I had it surveyed both structurally and mechanically before i purchased it as well and all was determined to be good for a boat this age/number of hours.

The problme has only happened twice; the first time the broker turned the key and nothng happened (i couldnt hear if the solenoid engaged or not as the engine hatch was closed). Second attempt it turned over but sluggishly (this was before the new batteries/cables etc). This past weekend, I went to start it a day after running it at 3500 RPM for an hour long cruise (plus some 1000-2000 rpm puttering) and the same thing happened. The only difference was that when it did catch (second attempt) the motor ran rough for about 20 seconds before smoothng out and then it ran fine for a 2 hour cruise.

My thoughts are to do the following;

• open the engine hatch so I can hear the engine and turn the key on to listen for the fuel pump to spool up in case it has an intermittent problem
• Turn the key and see if I can hear the solenoid engage (assuming it doesnt start right up the way it has the past 6-10 times I have run it)
• If the pump runs and the solenoid doesnt click-bad solenoid
• If the pump runs and the solenoid clicks and still nothing-bad starter
• If it starts as normal-pull out more hair and be paranoid as I only have one engine and boat in the Straight of Georgia

The rough idleing I am thinking could be my fuel possibly. The boat was on the hard for 18 months with about 1/3 tank of gas and I don't know if there was any stabilizer. Stabilizer was added and the tank filled full before moving it for the first time. My plan is to run it for about 10 hours and replace the fuel filter with a 20 micron filter and then do the same thing again until I have run all the gas through 3-4 filters. Then adding more stabilizer and refilling it (based on the advice of two different Merc mechanics and the Sea Ray dealer).

Any other suggestions?

 

[LTD.330]

The slave solenoids have a reputation for going bad. It's a $20 part and it is located under the plastic cover on top of the engine.

 

[koresample]

The slave solenoids have a reputation for going bad. It's a $20 part and it is located under the plastic cover on top of the engine.

Sorry for the dumb question, but what is their function and do they cause similar issues to what i describe?

Thanks,

Mike

 

[mvoellinger]

The solenoid connects the power to the starter when you turn the key. A bad solenoid will cause intermittent no crank situations, and will eventually give out and prevent you from starting the engine.

 

[testlab]

When you say it happened again, do you mean it turned over sluggish or it didn't turn over at all? If the latter then it could be the start in gear lockout is engaged. Wobble the shift lever back and forth a bit and see if it then engages. If sluggish then it could be bad connections at the starter solenoid or on the starter itself (or loose at the battery).

 

[koresample]

When you say it happened again, do you mean it turned over sluggish or it didn't turn over at all? If the latter then it could be the start in gear lockout is engaged. Wobble the shift lever back and forth a bit and see if it then engages. If sluggish then it could be bad connections at the starter solenoid or on the starter itself (or loose at the battery).

I didn't have to wobble the shifter at all, just turned the key to off then then back on (heard the alarm go and waited for it to stop) then cranked and it cranked over fine then caught, then ran rough.

I thought the solenoid was in the starter body which is why I asked about the slave solenoid. Looking at the manual for the motor, it looks like it has a slave solenoid on the motor, plus a solenoid on the starter body. I only thought there was ever one solenoid for a starter motor which is why I wanted to know what the purpose of the slave is. Is there a way to troubleshoot the slave solenoid, ore only by replacing it?

 

[testlab]

You may have low fuel pressure. Best to test it with a fuel pressure gauge.

 

[CliffA]

I thought the solenoid was in the starter body which is why I asked about the slave solenoid. Looking at the manual for the motor, it looks like it has a slave solenoid on the motor, plus a solenoid on the starter body. I only thought there was ever one solenoid for a starter motor which is why I wanted to know what the purpose of the slave is. Is there a way to troubleshoot the slave solenoid, ore only by replacing it?

i believe the slave solenoid is utilized to minimize the size of the wiring...when using DC power the size of the wire must be increased as the distance to carry the current increases...by interrupting (thus shortening) the distance between the batteries and the starter motor/solenoid combo with the slave solenoid the wiring associated with the engine starting circuit could be reduced in size....

as far as testing the slave solenoid, when someone attempts to start the engine you should be able to hear and/or feel the slave solenoid 'click' as the contacts in the solenoid make.....

cliff

 

[koresample]

i believe the slave solenoid is utilized to minimize the size of the wiring...when using DC power the size of the wire must be increased as the distance to carry the current increases...by interrupting (thus shortening) the distance between the batteries and the starter motor/solenoid combo with the slave solenoid the wiring associated with the engine starting circuit could be reduced in size....

as far as testing the slave solenoid, when someone attempts to start the engine you should be able to hear and/or feel the slave solenoid 'click' as the contacts in the solenoid make.....

cliff

A solenoid for the solenoid as it were. Ok, I looked it up in the manual for the engine and read the troubleshooting tips and I think you are right as it says if you want to try 'jumping' the slave you need to use 8 guage wire.

Thanks for the input, I will check it out this weekend.

Mike

 

[CliffA]

A solenoid for the solenoid as it were. Ok, I looked it up in the manual for the engine and read the troubleshooting tips and I think you are right as it says if you want to try 'jumping' the slave you need to use 8 guage wire.

Thanks for the input, I will check it out this weekend.

Mike

i keep a 3 ft jumper wire made with alligator clips on each end in my tool box on the boat...it can come in handy for things like this and jumping a failing trim solenoid if/when needed....by the way the 'trim up' and 'trim down' solenoids on the trim pump assembly are the same solenoid as the starter slave solenoid so they are interchangable....they are relatively cheap so i usually keep a spare solenoid in the tool box as well....

good luck....

cliff

 

[koresample]

i keep a 3 ft jumper wire made with alligator clips on each end in my tool box on the boat...it can come in handy for things like this and jumping a failing trim solenoid if/when needed....by the way the 'trim up' and 'trim down' solenoids on the trim pump assembly are the same solenoid as the starter slave solenoid so they are interchangable....they are relatively cheap so i usually keep a spare solenoid in the tool box as well....

good luck....

cliff

Great advice, thanks Cliff!

 

[Jimmy Buoy]

I had a similar issue a couple of years ago. Turned out to be a corroded ground terminal on the engine block. Once the large black ground wires were removed/cleaned/reinstalled no further issues. That being said there was a "click" from the slave solonoid when I hit the starter, there just wasn't enough juice going to the starter motor due to the bad ground.

 

[CliffA]

That being said there was a "click" from the slave solonoid when I hit the starter, there just wasn't enough juice going to the starter motor due to the bad ground.

very good advise....the 'clicking' from the solenoid is not 100% proof that it is working properly.....the best way to test the solenoid is to simply bypass it with a jumper cable to see if the problem is resolved....

cliff

 

[koresample]

So, I bought a slave solenoid as well as some contact cleaner. I found this site which has a ton of great troubleshooting tips http://www.sterndrives.com/no_crank_condition.html for the ignition and lots of other things.

I cleaned the starter contacts as well as sprayed cleaner into the switch from the key side (it's sealed) and now it starts every time. The one thing I can't figure out is when I turn the key, sometimes I get the high pitched buzzer from the engine compartment and sometimes i don't, but the motor kicks over regardless. What is the buzzer for? I can't find any reference to what this is.

 

[ardeprint]

. What is the buzzer for? I can't find any reference to what this is.

Thats most likely your fuel pump(s). It is priming your fuel lines and building pressure.

 

[rondds]

Buzzer meaning an alarm? or meaning a sound from the bilge area?
If the engine has adequate oil pressure, you won't get an alarm when you turn the key to the first position. This may happen if you just shut down and go to start up again - pressure hasn't had time to drop yet.

 

[koresample]

hi pitched tone from the engine area (I can hear the whir of the fuel pump) Happens when I do a cold start