Mercruiser 350 starting problem

slochner · Post by **slochner** » Nov 6th, '14, 21:51

Just reinstallled my Mercruiser 350s after 9 months of repairs (rotten stringers and bulkheads, rusted oil pan). Engines started well,I ran them dockside for an hour. All readings normal. Turned them off for a minute, and then neither engine would restart,even after several attempts. Boat is a B28, with original glass fuel tank, but no evidence of Ethanol problems. Tank was left virtually full during the rebuild, but engines seemed to run fine for the hour at the dock.

Would seem very coincidental for both engines to have clogged filters or failed coils at the same time.

Will check fuel tank vent line for clog in the AM. Any other thoughts?

Thanks.

Tony Meola · Post by **Tony Meola** » Nov 6th, '14, 22:36

I assume you are gettng spark at the plugs. If not start working from there. If you are getting spark,then you are not getting fuel.

Kevin · Post by **Kevin** » Nov 6th, '14, 23:32

Make sure your fuel tank vent is not clogged.

Yannis · Post by **Yannis** » Nov 7th, '14, 00:33

Open your fuel tank's cap and leave it open. If they start then it should be the vent.

Carl · Post by **Carl** » Nov 7th, '14, 09:51

Neutral safety switch?

Ground?
Tach wire shorting?

Gas line open?
Vent as mentioned..
Single tank...check the pickup tube...they can split or develop pinholes....but usually not both at one time.
Water in fuel?

Fuel line on mine one turned hard and would not seal. Had to replace, it was newer alcohol rated so I didn't think it would be effected...but it was.

Check for spark, check for fuel...
Let us know.

Carl

slochner · Post by **slochner** » Nov 7th, '14, 10:22

Morning after update:

Thanks for the replies. Both engines started this am. Will do another extended run at dock, while I am blowing out vent line. Will post results as they occur.

Steve

Tony Meola · Post by **Tony Meola** » Nov 7th, '14, 22:32

Is she straight carborated? Electronic ignitiion? If Electronic, it sounds like you might have a solenoid or a resister getting hot and not letting you strart it up.

Michael · Post by **Michael** » Nov 8th, '14, 21:14

Either vapour lock or an ignition component that is gettign hot and breaking down unitl it cools off.

slochner · Post by **slochner** » Nov 22nd, '14, 18:00

Thank you for the replies to date. Took the carbs out and had them rebuilt. Reinstalled and still have the same problem: both engines start well when cold and run smoothly. I warm them up and then turn off, and cannot restart. They crank but no start. Next proposed step is to get fuel pressure tester to hopefully determine if it is a fuel pump problem and/or vapor lock. Further thoughts?

Navatech · Post by **Navatech** » Nov 23rd, '14, 00:55

Do you have chokes?!... Might they stick?!...

Rocky · Post by **Rocky** » Nov 23rd, '14, 10:09

Thinking about this one. You stated 9 months fuel in existing tank sat. There is a possibility when your in a rich cycle (choke cutting air sending more fuel) engine would burn that, but if fuel's volatility is gone away and your out of the enrichment cycle/warm engine it might not burn it. This happened on a injected engine of mine at work but the principle still exists, new fuel cured warm no start. I'd try a separate gravity fed 5 gallon tank of fuel sitting on other engine box or bridge right into carb inlet and try cold to warm cycle again if you haven't tried NEW fuel as of yet, just one more elimination of the big three an engine needs to run.

John F. · Post by **John F.** » Nov 23rd, '14, 11:04

My B31 with 454s had rubber fuel lines to the carbs, with inline filters in addition to the Racor spin-ons. I used billet aluminum filters from Summit Racing for the in-lines. I also had a set of clear glass filters (not approved for marine use) that I'd put on when I thought I was having fuel problems. Just a thought if you have rubber lines. Its pretty easy to see fuel flow with a glass filter.

I'd also check spark. As I remember, cold starts OK, hot starts not, could be coil. Coils can be bench tested. What ignition do you have? My original Thunderbolts did this also when they died. I replaced the whole system with an electronic system bought aftermarket that included distributor, coils, wires.

Good luck

Rocky · Post by **Rocky** » Nov 23rd, '14, 11:08

Forgot to mention an observation I have about your issue.
Mechanical- not common
Ignition- not common, at least with my Bertram the ignition systems were separate systems not related.
Fuel- common. Both share same fuel, and source to get fuel to both engines from pickup.

John F. · Post by **John F.** » Nov 23rd, '14, 17:01

Yeah, I should've read better. If its both motors, its got to be fuel between the tank and the pumps.

Tooeez · Post by **Tooeez** » Nov 23rd, '14, 21:32

This has me thinking, probably because it's the kind of weird problem I always seem to have. You said you shut the engines down; if they are not stalling out before they don't start I don't see how it can be a fuel supply problem--if there is fuel in the carb bowls at shutdown there is no way I can think of that they could be empty a few seconds later when you try to restart. It's easy to check--look down the carb throat and pump the throttle--if the accelerator pump gives a shot of fuel gas is present. Rocky may have the answer with degraded gas--try closing the choke manually and see if it runs. If not it then has to be an electrical problem. The re-installation may be the cause--I know that I, despite taking every precaution, making diagrams and taking photos, have made mistakes in hooking things back up. I can't think of any wiring issues that would cause what you describe, but it happens to both engines, and the only thing common to both is fuel and re-installation--if it isn't one it has to be the other. You might want to try hot wiring a coil direct to the battery--if it starts then you know where to look.

STraenkle · Post by **STraenkle** » Nov 24th, '14, 14:00

Like most have said, the only thing they have in common is the gas tank. However we have a couple assumptions:
A) both engines only shut down when to turn them off, they don't stall on their own.
B) both are on different batteries and kill switch/ignitions
C) when you try to restart, both are cranking over at a good speed
D) both have spark and fuel when you try to restart

If you shut only one down, can you start it again? Are either running hot and making the engine room very warm? I kinda like the clogged fuel vent idea. While the engines are running, the might be able to over come the vent clog, shut them down and the negative pressure sucks the fuel back into the tank, then when the pressure finally equalizes, the engine will start again. I would run them off a six gallon tank directly and by pass the tank.

However it is possible that both engines sitting for so long have similar issues. The only time I have ever had an engine that would start cold, but not warm was a weak coil. I changed to the summt coil and distributer, the Mercruiser one was $600 bucks and would have take 4 months to get.

If the engines crank, but very slowly, battery or Starters may have gone. I would try only shutting 1 down and see if you can get the other one started back up.

Harry Babb · Post by **Harry Babb** » Nov 24th, '14, 18:50

May be I missed it but, is the ignition Electronic or Breaker Point Ignition?

hb

slochner · Post by **slochner** » Nov 28th, '14, 20:41

In response to Scott's posting, I believe your assumptions A-D are all correct.

Have further data to report: when engines run for 15 minutes and reach normal temperature, the choke plate on the primary barrels on both carburetors opens approx. 45 degrees. When I shut off the engine for 1-2 minutes and went to restart, the choke plate did not open at all, engine would not start, and gas appeared to fill carb throat and rise up to the level of the choke plate.

Could spray painting the engines have inadvertently affected the performance of the coiled metal thermostat which activates the choke plates?

Navatech · Post by **Navatech** » Nov 28th, '14, 23:44

slochner wrote:when engines run for 15 minutes and reach normal temperature, the choke plate on the primary barrels on both carburetors opens approx. 45 degrees.

Being a grease monkey of the diesel species I'll be the first to admit that I don't really know that much about gas engines... Having said that, the above sounds wrong... A 45 degree on the choke would still "choke" the engine so I would expect the choke to fully open when the engine reaches operating temperature...

slochner wrote:When I shut off the engine for 1-2 minutes and went to restart, the choke plate did not open at all

Again, with the above caveat, this sounds wrong... Mechanical automatic chokes are usually "wax" operated... Like thermostats... Due to the temperature the wax expands and this expansion powers the levers that operate the choke plate... I would expect the choke plate to close only when the engine cools significantly below operating temperature... No way that happens in "1-2 minutes"...

slochner wrote:Could spray painting the engines have inadvertently affected the performance of the coiled metal thermostat which activates the choke plates?

The coil should NOT have been painted... But a thin layer of paint shouldn't be a problem... You earlier stated that you had the carburetors rebuild... Any such concern would (should?) have been addressed at that time... As the problem occurred both before and after the carburetor rebuild my guess is that there's an issue with the coil (and/or the return spring against which it operates) as it's not common to replace these in a rebuild...

HOWEVER, if the coil was painted with (way) too much paint, to the point that the coil can't expand/retract (i.e. basically the coil is prevented from expanding/contracting) it has been made inoperable... If that's the case I suggest you use paint remover (or brake fluid) to clean off ALL the paint or replace the coils with new ones... To clean them properly I would dismantle them and let them soak in paint remover (or brake fluid)... Rinse and repeat if necessary until you get a completely clean coil...

Carl · Post by **Carl** » Nov 29th, '14, 09:40

All that, I'm not a mechanic stuff Navatech said....along with I do not even work on diesels.
But I have had my share of troubles thru the years.

Choke closing appears to be the issue...or at least a big big issue.

Almost sounds like they are working backwards...

If it was me...I'd start and run cold, shut it down. Let's chokes close as you say they are, then try to start.
Pretty sure you'll see the same thing...no start solution.

At that point I'd disconnect the choke linkage and tie off choke in open position and try to start.
If it starts you now know that's your problem.

I would not start off by tiring choke open for two reasons.
One, we need to have the exact problem present to fix it.
Two, wide open chokes can be a pain to start when engines are cold.

If it starts....

Now it's time to figure out why chokes not working.
Linkage hooked up wrong...
Bad ground...
Calibration off..
Wrong choke...

I am just guessing reasons chokes not working here as you might tell.
But for me the important part is getting them running again after they shut down and won't start.

John F. · Post by **John F.** » Nov 29th, '14, 10:12

Or instead of disconnecting the choke just hold it open with a screwdriver or your hand and start the boat. If I were going through these problems, and you may have already done so--I'd get a remote start and disconnect the carb linkage so I could control everything from down by the motor.

If you think its a fuel problem on the restart, try spraying some cold start stuff in the carb (ether or whatever that stuff is). If its lack of fuel, it'll start and die. If it doesn't start, its ignition, but why two separate ignitions fail at the same time is beyond me. Actually, most of this stuff is beyond me. Good luck.

Navatech · Post by **Navatech** » Nov 29th, '14, 12:44

Both Carl and John F. make a valid observation... It's very easy (and not destructive in any way or form) to open the choke flaps manually... In order to narrow down that this is indeed your problem I suggest that you warm up your engines and then shut them down... Wait your "1-2 minutes" and try to restart them... If the problem still exists your next step will be to remove the carburetor's flame arrester... This will allow you to manually operate the choke flap... While you could do this by hand I recommend using a long(ish) screwdriver... The reason being a possible back fire... That's THE reason your engines have flame arrestors... You don't want to burn your hand!...

Also and quite importantly, by removing your flame arrestor you will have removed a VERY important safety measure... Make sure there are absolutely no gas fumes when you start the engines with the flame arrestors removed!...

If you don't have a second hand to help you to start the engine while you're holding the choke flap and you don't have a remote starting setup you can use some very thin rope or wire and some duct tape to keep the choke flap open... Having said that, a remote starting switch is cheap and very handy!...

OK, now that we have the logistics out of the way there are two possible results...

1) The engines start just fine... This means you found your problem... You have two avenues for fixing this:
1. A) Use paint remover (or brake fluid) to clean off ALL the paint or replace the coils with new ones... To clean them properly I would dismantle them and let them soak in paint remover (or brake fluid)... Rinse and repeat if necessary until you get a completely clean coil...
  B) Replace the coils and return springs with new ones...
2) The engines still don't start... This means we'll have to go back to the drawing board and do some more thinking...

STraenkle · Post by **STraenkle** » Nov 29th, '14, 12:58

The choke at full temp should be all the way open. sounds like the only thing holding them at 45% is the engine running and probably running quiet rich. you shut it down and the choke goes closed, you will flood the engine when you try to restart. The choke is fully mechanical? If it has a wire running to them, just by pass the choke, loosen the 3 screws holding the adjustment, rotate till the choke is all the way open. If cold when trying to start, pump the gas 5 or 6 times, crank and keep pumping once it starts to fire, do that till engine will idle. When hot turn the engine, if it doesn't start push the throttle to half or full (lets more air than gas in) till you hear it start to go then back down quickly.

The old fully mechanical have a spring case attached to the intake. Once rust gets under them (or paint), the heat does not transfer and the choke stays on. It is not hard to start them without choke, just takes a little practice, or clean the rust might work. if they have a wire to them, then the choke may not be getting power, or out of adjustment. To start, I would disconnect the choke and see how well that works for you. Sounds to me like they are just flooded at operating temp and even at 45 degrees open, the engines are running very rich.

Rocky · Post by **Rocky** » Nov 29th, '14, 18:05

[URL=http://s379.photobucket.com/user/r ... .jpg[/img][/url]
[URL=http://s379.photobucket.com/user/r ... jpeg[/img][/url]

Assuming you do not have the top carb setup, I believe you are describing you have a bi-metallic choke stove(lower pic) in which contracts when cold and expands in nature when warming/hot, pushing/pulling a linkage to choke plate. If you don't have the shield over it to contain necessary heat to make it work, and you've painted it, that would make a lot of sense that system was working before you did all that work to your engines and stringers, now it is not. Another question to consider- when you hooked up the linkage from stoves to carbs, are there any other holes in choke linkage you might have put linkage rods to possibly? Again this happened to both engines so trying to see the big picture here and that is both engines with same issues. Likelihood of both stoves if that is what you have, going bad statically sitting while you did your engine work is slim. John's screwdriver trick has been done many times, quick and dirty test.

jspiezio · Post by **jspiezio** » Nov 30th, '14, 08:10

Pictures like those Rocky posted would be really helpful. Then everyone knows which carbs are on the engines and what their condition is.

Carl · Post by **Carl** » Nov 30th, '14, 08:41

Just choose a screwdriver that can't fall into carb and wedge lightly.

Preston Burrows · Post by **Preston Burrows** » Nov 30th, '14, 08:53

Some good long answers here!

Disconnect the chokes and see if that pins down the re-start issue, then either clean the choke springs or replace with new or electric chokes!

I hate chokes.

Carl · Post by **Carl** » Nov 30th, '14, 14:25

Preston Burrows wrote: I hate chokes.

Luckily for you, being the Bahamas you don't need the buggers

Tooeez · Post by **Tooeez** » Nov 30th, '14, 22:31

You said gas appears to fill the carb throat to the level of the choke? Do you mean the carb is filling up with liquid fuel? If so, the needle valve on the float is not sealing. Did you change fuel pumps? Fuel pressure too high can overpower the valve.

slochner · Post by **slochner** » Dec 1st, '14, 14:57

Hooray, Hooray! I believe we have found the problem - the housing of the divorced metallic coil housing was put in backwards, so that the linkage to the choke assembly was installed on the wrong side of the coil. As the engine warmed up, the choke plate was closed more firmly, not opened. Currently waiting for engines to cool so that I can confirm fully operational chokes. Thank you all for your patience and input. Steve L.

Navatech · Post by **Navatech** » Dec 1st, '14, 15:24

slochner wrote:Hooray, Hooray! I believe we have found the problem - the housing of the divorced metallic coil housing was put in backwards, so that the linkage to the choke assembly was installed on the wrong side of the coil. As the engine warmed up, the choke plate was closed more firmly, not opened. Currently waiting for engines to cool so that I can confirm fully operational chokes. Thank you all for your patience and input. Steve L.

THAT should fix it... It should also result in lower fuel consumption...

Rocky · Post by **Rocky** » Dec 1st, '14, 16:40

Great news Steve, hope you have happy engines when warm now!
There's that symetrical issue with both, identical problems.

Navatech · Post by **Navatech** » Dec 2nd, '14, 00:36

The one thing I have been pondering is that this happened both before the carbs were rebuild and after the rebuild... And I don't think that this was the issue prior to the rebuild... You would have noticed a fuel consumption of 20-30% above normal... So, I'm thinking there was another issue with the carbs before the rebuild... That was fixed by the rebuild... However, the rebuild introduced this new issue...

BTW, I would put the carbs rebuilder on my personal black list... No way somebody who builds carbs for a living should make such a mistake!...

And no, I wouldn't change to electrical chokes... KISS!... Especially in the harsh marine environment...

STraenkle · Post by **STraenkle** » Dec 2nd, '14, 11:06

I don't know if I would put the carb rebuild guy on a black list,more than likely, the mechanical choke attached to the intake did not go to the carb rebuilder. Likely the linkage was just disconnected when he removed them to send to the rebuilder and left the spring choke attached to the block.

Navatech · Post by **Navatech** » Dec 2nd, '14, 11:18

STraenkle wrote:I don't know if I would put the carb rebuild guy on a black list,more than likely, the mechanical choke attached to the intake did not go to the carb rebuilder. Likely the linkage was just disconnected when he removed them to send to the rebuilder and left the spring choke attached to the block.

You raise a valid point... IF the carbs were not sent with the choke actuator then the carb guy is certainly blameless...

slochner · Post by **slochner** » Dec 2nd, '14, 12:12

Rebuild Man totally blameless. The coil element stayed on intake manifold during carb rebuild. The mistake was made way back in March when my good friend and I painted the engine, and, in so doing, removed the coils and housings from the intake manifold. Mea Culpa.

Rawleigh · Post by **Rawleigh** » Dec 2nd, '14, 12:16

Let the self flagellation begin!! We have all done something like that before. LOL!

Carl · Post by **Carl** » Dec 2nd, '14, 12:59

Rawleigh wrote:Let the self flagellation begin!! We have all done something like that before. LOL!

Not me!! never!

Okay, hardly ever.

Would you believe....

Look at the bright side...you got two rebuilt carbs out of it!
Well you did pay for the rebuild...and they may not have needed a rebuild...but hey I am sure they will run better and well worth it in the long run!

Its all good.

Navatech · Post by **Navatech** » Dec 2nd, '14, 21:14

All is good that ends well... Having said that, I think this proves the need for including pictures with posts such as the original post... Also, it's necessary to detail work done prior to the problem rearing up its ugly head... Chances are good that with the background information and the pictures somebody would have come up with the solution without having to go to a carb rebuild...

Anyway, the rebuild carbs are only going to improve your fuel consumption!...