Fuel problems? 88 40hp Johnson

josh_scci · Sep 15, 2010

Ok so I took the boat out for one last weekend on table rock and a weird problem popped up. First of all the carbs where just rebuilt at the shop so I don't think they are the issue also the fuel line was replaced as well with an attwood replacement. Now the problem is the motor surges but not all the time and only at WOT. Sometimes if I was to shut it off and turn it back on the problem would go away and other times I would have to pump it manually a few times before it would go away. At other times it would run just fine all day with no issues. I suspect the fuel pump needs rebuilt, but it almost acted like something was clogging the fuel pickup in the tank intermittently. What would be your first choice as the problem? Also what size fuel lines am I supposed to have?

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

OK i was just checking on parts info so I went out to get the exact model number and it is J40ELCO and that shows up as an 1985 model but my tittle says 1988. I just double checked the freeze plug and it matches the
J40ELCOB on the id plate. Also I found this while looking around at the motor what could it be and why is it disconnected?

Al-53 · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

If I am not mistaken the brown wire goes to temp sensor in the head....look for the other end in the top of the head...or if that one is Connected to the head....you need to find the other wire to connect it to.....It goes to the over heat alarm in the control box....

Al

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

OK I think that must be disconnected because the VRO is long gone on this motor. I bet the mechanic disconnected it and taped it but the tape came off.

Anbody have any ideas on my fuel problems?

Daviet · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

It looks like the temp sender that AI-53 suggested. It has nothing to do with the VRO, it's for engine temp and should be hooked up. Turn the key to the on position and touch the knife connector to gronud on the block, the overheat horn should sound off.

Al-53 · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

the temp sensor has nothing to do with the VRO as far as I know...its there to alarm you your engine is over heating.....not a low oil alarm..those wires are on the VRO unit or tank..

Follow that wire and see if it goes to the head area,,and a sensor behind the wire.....recessed in the head

Al

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

OK i will check that stuff out. This was my dads boat before he passed away and I'm inheriting a lot of problems he seemed to neglect like using a reputable mechanic. I am sure it was the mechanic that disconnected that wire because our VRO went out and the alarm was sounding and the boat wouldn't run. SO he took i out for us and we never heard the alarm again. I think i was 16 when that happened and I'm 29 now so it has been a while.

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

you all where correct I grounded the wire and the alarm sounded, but there is no place that I can find to hook it back up and I don't have any kind of manual for this motor. Anybody got any ideas. Also is the fuel pump mounted to the back of the intake manifold? If so it looks nothing like the part diagram on the parts list I was looking at.

Al-53 · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

look for a wire in the head area.....should be same color.....that would be the temp sensor....for piece of mind i would get that working correctly..the mechanic maybe just unplugged it since the sensor was broke....and did not want to replace it....

Now your best bet is if your going to work on the engine get the Shop OEM manual from Ken Cook....not a haynes or soltec one...cost a bit more ..but the OEM is all your motor and not a bunch of different ones...

One fix from the manual pays for its self..most shops charge 80-90 a hour labor..

fixing the temp alarm may save u big money in the long run....you will know your motor is running hot..the way it is now you have no warning and can cook the engine....

Usally on that motor the sensor is top right corner looking at it straight on....and a wire coming from it....

Al

Daviet · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

#78 is the temp sender, should be near the top of the cylinder head.http://www.ishopmarine.com/ishop/jsp/AsplIsmCcatViewBase.jsp?&lvlCode=5&pCode=C0190954&path=BRP~A0000008~M0010606~M0010684~M0010685~C0190954&isFromCMS=false&hideAdd2CartButton=&isStandAlone=&is4CmsShop=&reqln=Unknown&reqem=Unknown&reqph=Unknown&reqFor=29&req4Browse=1&docId=&docName=&isForSupStore=false&cCatFilter=&eCatSupFldr=

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

OK there is a wire the same color going into the hole where the sensor should be. If you look at the picture it is the one that comes out from behind the red wire and goes up and it has some kind of black sleeve on it a little higher up then it goes into the cylinder head. The problem is I cant see anywhere the two wires have been cut or anything.

Daviet · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

So you are saying that the brown wire with the blue crimped knife connector and the black insulator tube goes to the temp sender in the head? Look at the wiring harness coming from the red cannon plug under the starter solenoid, there should be a brown wire coming out of that harness that connects to the brown wire from the temp sender.

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

I think the wire may have been cut or disconnected from each other because I can't see the other end of the two brown wires. When I get a chance I'm gonna pull the wiring harness apart and see where the other ends of those wires are.

Does any body have an idea about the fuel pump? Would it have been switched to a different model since the vro was taken out? If so how do I get a rebuild kit for it?

Daviet · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

If the VRO has been removed the fuel pump would have been replaced with a pulse type pump, which one is up to the person installing it. Can you post a picture of the pump you on the engine now?

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

OK so i pulled of the electrical tape to see where the two wires went and this is what I found they go back and then are joined togetherwith what looks like a hard plastic shrink wrap and they come out the other end as one wire?

And here is the fuel pump I think?

Daviet · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

It looks like the temp sender is hooked up to the harness, I have no idea why there is a pigtail spliced into the system. Someone may come along and have some better advice. I would cut it off or tape it up into the harness. It looks like some one may have bypassed the oil side of the VRO, not eleminated it completely, you are still using the fuel pump side of the VRO.

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

Any ideas on the fuel pump?

Daviet · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

As I said in the last post, it looks like the VRO was not removed. The oil side must have been bypassed and you are still using the fuel side of the pump.

josh_scci · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

I am a big dummy here so I don't mean to sound stupid, but what does that mean for me in terms of fixing the fuel pump? Should I replace the whole thing or should I just rebuild it with a repair kit, and what parts do I need either way?

Daviet · Sep 15, 2010

Re: Fuel problems? 88 40hp Johnson

Have you checked the fuel pump pressure, why do you think it needs to be replaced or rebuilt.
Since the oil side of the VRO has been disabled, it would probably be cheaper to remove it completely and replace it with a pulse type pump.
This topic has been covered on the forum in the past, look in the "Top Secret Files", there is a post there.

Fuel problems? 88 40hp Johnson

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