More Outboard Engine Troubles Part 2 - Long

[tryhard]

G'day All & thanks to those that offered their opinions previously.

Thought I'd give you some feed back following some of the things that I did today.

For anyone reading this post before the original here's a quick overview.....

Suzuki DT85 (early 80's) motor ran for 1/2 day mostly at slow speeds - toward the end of the day, motor started stalling when put in gear.

Eventually, motor refused to start & on water checks were done for fuel & spark - preliminary assumptions were that the motor was flooding.

following various opinions & advice from members, here's a rundown on today's investigations : -

1. warmed motor up & did compression check with all spark plugs removed

top Cyl. 140 psi

Middle 150 psi

Bottom 150 psi

Now I dont vouch for the accuracy of my gauge as the last time it was compression tested (someone elses gauge) readings were between 125 & 130 psi ? What I can now be confident in is that the readings are not too far apart so no anomilies between cylinders is I believe a reasonable assumption. (3 readings per cylinder)

2. Went and bought new plugs - asked the service centre what the gap should be & rec'd the reply that they are good straight from the box. I persisted & was told that gap should be 0.9mm (0.035" by my calcs) - checked new plugs & found each one to be set @ 0.025" - re-gapped plugs.

3. Checked to see if there were drain plugs on the carby fuel bowls - None

4. Tilted motor all the way up & pumped the primer bulb to see if it was possible to tell if same amount of fuel came from each jet. with my untrained eyes, I was not able to tell - looked the same to me !

What I did see however was that when I sqeezed hard, there was fuel squirted from the carby 'over flows'?

5. whilst in the full up position, I squirted carby cleaner at the jets & then let it drain.

6. I disconected the fuel inlet hose for each carby & squirted carby cleaner into each one (unsuccessfully I think) - I'm going to have the carbies rebuilt so if I ended up moving gunk & causing more blockages I figured all I would achieve is complete justification for full service by the professionals - right ?

7. cleaned up fuel & carby cleaner from motor & left to drain & dry for an hour or so.

8. came back & turned the motor over ( no plugs in ) - then put plugs in reconnect fuel from main tank & final check before starting..........this is where it gets a little interesting

9. connect muffs & started motor - motor runs 3 minutes - hunts for fuel & dies - re-start motor, motor hunts after about 3 minutes - squeeze priming bulb to find it's gone soft - motor continues to run then dies again - RE-START BLOODY MOTOR - you get the picture.

10 New tact required ! - connect aux. tank place on ground next to boat - start motor, motor runs about 5 minutes this time, hmmmm, re-start motor motor runs about 5 minutes, Hunts for fuel - squeeze primer bulb & motor continues to run five more minutes then hunts & dies. I can see a pattern here........

11. Re-locate aux. tank to rest on topside of boat slightly higher than motor RE-START DAMN MOTOR AGAIN -this is getting tedious.......motor runs & runs & runs - stopped timing after 25 minutes

12. whilst the motor is running I remove the bottom plug lead & note motor changes tune - re-connect ow! ow! ow! bottom lead & disconect middle - no noticeable change in tone - interesting & not what I was expecting re - ouch, connect & remove top lead - no noticeable change in tone ......

anyone want to comment on this? I thought I'd get a noticeable miss for each cylinder????

13. pulled plugs for a look, Oh yeah, I did actually shut the motor off first - hopefully the pictures will show the results,

the bottom plug had quite a fair bit of carbon whilst the middle & top were a little darker than I'd anticipated.

I believe that I have possibly got an issue with the fuel pump, I thought that the motor should drag the fuel up from the aux. tank on the ground & plus the fact that when raised to slightly above the level of the motor there was no problems.

All this plus the fact that it was not dragging the fuel from the main tank. Am I jumping to conclusions ??

I will now need to pull up the floor & check all the connections & hoses for the main tank and I will review my filter set up as well.

[Shark Bait]

Your motor is starving for fuel. Your primer bulb going soft suggests there is a vacuum in your fuel line. Make sure your tank breather is breathing. Make sure your fuel supply line is not blocked or kinked. Does your fuel bulb go soft because it is old? Placing the auxilery tank above motor removes all vacume in fuel line by supplying gravity feed.

In summary,

Check fuel vents & breathers in tanks.

Check fuel line is not kinked or blocked.

Check condition of fuel bulb.

Check/change fuel filters.

Last, check fuel pump. They have a filter screen in them & the manual suggests they should be serviced via the maintenance schedule. This gets overlooked until the pump fails.

As far as the condition of your plugs go, your bottom cylinder is doing more work than the others. This could be idle mixture or linkage adjustment (Ballance). Dealers seldom touch carby linkages because it is a time consuming exercise. If you want a happy, reliable motor, you'd best get your carbies serviced & set up properly. This may mean pulling them down, cleaning them & setting float levels, idle stops, mixtures & linkages.

[tryhard]

Your motor is starving for fuel. Your primer bulb going soft suggests there is a vacuum in your fuel line. Make sure your tank breather is breathing. Make sure your fuel supply line is not blocked or kinked. Does your fuel bulb go soft because it is old? Placing the auxilery tank above motor removes all vacume in fuel line by supplying gravity feed.

In summary,

Check fuel vents & breathers in tanks.

Check fuel line is not kinked or blocked.

Check condition of fuel bulb.

Check/change fuel filters.

Last, check fuel pump. They have a filter screen in them & the manual suggests they should be serviced via the maintenance schedule. This gets overlooked until the pump fails.

As far as the condition of your plugs go, your bottom cylinder is doing more work than the others. This could be idle mixture or linkage adjustment (Ballance). Dealers seldom touch carby linkages because it is a time consuming exercise. If you want a happy, reliable motor, you'd best get your carbies serviced & set up properly. This may mean pulling them down, cleaning them & setting float levels, idle stops, mixtures & linkages.

Thanks Shark bait,

pretty much what I suspect.

do you know if the pump should be able to drag the fuel up from the height of the leg say 20 + inches ?

During the exercise when I was running of the under floor tank, I had the filler cap Open - so even if the breather was blocked, it would not hav made any difference !

Primer bulb is pretty new but I think I'll replace it any way.

[a boat]

Hi Tryhard, a operational fuel pump will have not problem pulling fuel the height you mention. Reading your post the bit about not having an affect when you remove the high tension leads from the top and middle cylinders is a worry. If running correctly when you remove one lead at a time(be careful not to be zapped) it should make a difference in engine running with each cylinder. Something not right there and I would be removing and servicing the fuel pump and same with the carbies if it was my engine.

Do that and let us know what you find.

Cheers,

Huey.

Edited January 16, 2008 by Huey @ Huett Marine

[paulg]

Try hard, in my opnion check the connection/fitting between the fuel line and the petrol tank.

One of my previous motors decided to stall in the middle of botany bay. when i looked at the hand pump it had sucked inwards, i cut the fuel line fitting off and held the fuel line in the petrol tank by hand and this got me home.

empty the clear fuel bowl before the petrol pump to half way,

get some one to hold the fittingless fuel line in a container of petrol, and start the engine.

If the petrol pump is working the clear fuel bowl should fill up straight away. If the blockage was is in the fuel connection the engine should continue to run.

This problem occured to me without warning and the engine had not missed a beat the week before.

cheers.

Hi Tryhard, a operational fuel pump will have not problem pulling fuel the height you mention. Reading your post the bit about not having an effort when you remove the high tension leads from the opt and middle cylinders is a worry. If running correctly when you remove one lead at a time(be careful not to be zapped) should make a difference in engine running with each cylinder. Something not right there and I would be removing and servicing the fuel pump and same with the carbies if it was my engine.

Do that and let us know what you find.

Cheers,

Huey.

[Harris]

Hi Tryhard,

If your fuel line is getting on a bit, check that its not delaminating. i.e. the inner core has separated from the outer core and therefore sucks in blocking the flow of fuel if theres enough resistance to supply further down the line. I know it sounds like a longshot but I got caught with it on a car once.

Cheers,

Anthony.

[pirate pete]

I once had a problem where my motor was starving for fuel similar to yours, squeeze the primer rock solid boat gets up on plane then dies several mins later , turned out to be fuel pump problem, the rubber hose from the crank case to the fuel pump had a crack in it and once replaced solve problem.

Pete

[tryhard]

thanks to everyone for the responses.

At this stage, I'm pretty much resigned to getting the carbies rebuilt & set up properly and I'll get the pump done as well I think.

These will be the 1st things to isolate, then at least I know there done.

I'm reasonably sure the fuel line has not delaminated as I have replaced this in the last 18 months or so.

As money does not permit at the moment, I will do the simple checks suggested before moving on the the more costly items.

regards

[tryhard]

SUCCESS !!!!!!

1st, thanks to every one who offered advice.

Following Huey's comment that the fuel pump should draw fuel from the Aux. tank when it is sitting on the ground next to the motor, I decided to rebuild the fuel pump.

Completed that this morning, cost $80 for the Kit - pretty pricey for 2 diaphrams and a spring !!!!!!!!!!!

took about 40 minutes from removing the pump to refitting.

I have run the motor this morning with the auxillery on the ground - No Probs

Ran the motor from the main tank - No probs.

Only one issue........ Broke the b$#@ filter / separator - thought I'd drain the fuel & watch it fill from the main tank but managed to pull up the main bolt too tight shattering the glass bowl -bugger bugger bugger.

I was going to change it but was not planning on right now.

Any way next test will be on water - maybe tomorrow - see what happens.

[Shark Bait]

Hopefully, when you disconect your plug leads 1 at a time, all 3 cylinders will get a more equal result. If you have a weak fuel pump, the way your carbies are plummed, the lowest carbie will allways recieve fuel before the next highest.

Described another way, if your motor uses more fuel than your pump supplies, the bottom carbie has first pick of the fuel until it's full. Only when your lowest float bowl is full will it let fuel go to the middle carbie, & the highest gets fuel last.

Hope this makes sense.

Good luck.

[tryhard]

Thanks Shark Bait,

Makes perfect sense - Pelican Had already pointed this out to me.

Took it out on the water this morning.

All seemed to go well and then, I had the same problem re-occur.

This time when I pulled the plugs they were dry.

The motor refused to start at all.

I pulled the air box off & sprayed a bit of 'Start Ya bastard' but the motor only ran on that & did not run on the petrol - that is it refused to keep going.

I put the 2 new spare plugs I had in & that seem to do the trick (even though the plugs that were in there were also new.

once going, the motor ran fine again - called it a day at that point.

When I got home the motor started on the flusher but there was a definite miss then she stalled as though it was out of fuel & I could not restart it.

I have given up for now, next stop is the mechanics.