Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

[ezeke]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

18-7800 is the Sierra Repair kit.

18-7352 is the Sierra replacement pump.

OMC pump # 433387 has been superseded by BRP pump # 438556.

BRP has a repair kit # 438616.

433387 was used as a stand alone fuel pump on engines as big as the 140HP until the VRO came out - see the 1980 140HP parts diagrams.

 

[perkdp]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

My opinion is, you've found your problem

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Perk,

That's what I wanted to hear.

Ezeke, The pump is very simple to rebuild...takes 2 minutes to take it apart, and the same to re-assemble...

I'm just wanting to know if this would cause the problems I've been having.

Thanks for the info.

Shawn

 

[mikesea]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

shawn,I think you hit paydirt,heck,sorry about the pulse port,totally forgot about those older engines having the port right behind it with the gasket making a seal,the SPL is the tipoff,no VRO on those engines,that was a transition period and many of the "special "engines were used commeccially.You may have to use an earlier year like 1985,for a rebuild kit for the pump,anyway I believe when you put the new parts in you will have a new engine,sorry about the wild goose chase ,but at least you know you have alot of things that are good LOL, FYI,some engines have a third hose that goes to a pulse port from the fuel pump, those engines have a different type of set up

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Mikesea,

I have researched (and been told on this post) that the part I need to rebuild my kit is the 18-7800 from Sierra.

After looking at that part, there is a 'wheel' looking gasket included, that I don't see in my fuel pump. I'm wondering if it is kind of a universal kit that you may or may not use all of the parts out of, or if my pump is missing something.

It appears to have all of the other parts I'll need.

Thanks for the help guys - hopefully I'll have a rebuild kit in my hands on monday or tuesday, and can go from there.

I will update when I rebuild the fuel pump, and let you know how it goes.

SQ

 

[fireman57]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Shawn, I believe that in one of your two or three threads about this engine you stated that when you pumped the primer bulb that the engine would pick up and that someone told you that it was probably a faulty fuel pump. I am not an OMC mechanic, or anything of the sort but do work on the 75hp and down on the side. You started a different thread each time something else popped up and you should have stayed with the original thread. Most of the guys here are real mechanics in this field and give their advice for free. If you stay with the original thread they can see what has been done, the results from the advice given, and they they can go from there. I know that you recapped what you had done up until now but (I should have checked first) I know that someone would have suggested pumping the primer bulb to indicate a faulty fuel pump. I'm glad that you found your problem, and I truly believe that you did, but I think you would have found it sooner had you stayed with the original thread. Please don't take this as a flame as it is not meant to be that in any way, shape, or form. I also ask that you stay active in this forum as you have been through a lot and hence, have a lot to give.

 

[mikesea]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

yep,those kits are often universal,for the sake of such a minimal cost,they include enough parts to cover a few different applications,you find this alot with carb kits too,the wheel part your talking about is for the front fuel inlet cover

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

First of all,

Thanks again for all of your help. I am going to have the fuel pump rebuild kit in my hand on Tuesday AM. Will install it at lunch or sooner, and hopefully head to the lake that evening! I'll keep you all posted!

Fireman,

Honest reply and I understand it fully!

As an owner/operator of a message board/forum of my own for TX Land-based Shark fishing, and any other type of fishing... ( http://www.lonestarsharkers.com ), I've realized that once a post gets enough replies...and nothing seems to get resolved, people tend to move on to the newer posts. This isn't necessarily the case here...but it is part of the reason why I started another thread (habit?)

A LONG time ago, I had bad fuel lines (when I first bought the boat), and I had to pump the bulb to keep it running at times. However, I replaced the entire spanse of fuel lines, every hose on the boat, and it fixed my problem, for then.

Now, almost 2 years later, pull the boat out of the shed and I again have a rough idle/starving situation. I hadn't cleaned or rebuilt the carbs since I had owned it, and wasn't sure if the previous owner did...so I tore it off and asked a family friend (30+yrs OMC mechanic) to guide me through a rebuild of the carbs. That went smooth, and I figured all was well.

First time I ran it on the hose, had the same problem. I went to check spark and got shocked by the plug boot (bad sign). So, I instantly assumed electrical, and posted up. If the plugs wires were arcing, they needed to be replaced either way as the excessive resistance can't be good. So, changed the plugs and plug wires. THEN, I had a starter issue! Go figure. Replaced the starter drive kit, and went to the lake...had the same rough idle/starving issue. It wasn't until the lake trip that i realized that priming the fuel bulb got my idle smoothed out and made the engine run correctly. So, now I am instantly thinking fuel related issues again...although I know I have replaced everything short of the pump. Several people told me they thought it may not be the pump, because it runs good at high RPM. That baffled me as well.

However, Because I NOW thought it was definitely fuel in lieu of electrical problems, I posted up a new post regarding FUEL issues. I figured some people know fuel, some know electrical, and some hate one or the other. All of the fuel issue gurus would hop on and help (and they did), and the electricians wouldn't bother wasting their time anymore. Those who know it all, reply to all of them anyway...new post or not.

And, after all of this, you are probably wondering, So why not go see my friend who is an OMC mechanic?

Unfortunately, that same family friend went into the ER the SAME EVENING after helping me complete my carb rebuilds. He ended up with a ruptured spleen among a few other things, and just got out on Friday (10 days I believe?). I haven't had it in me to call and bug him yet! :$ o

So, I figured I'd post up again...and I think I may have finally kicked it!

In the future, I'll try it all on one thread. But, because my posts tend to be long-winded...if I find something that veers off the original title, I will sometimes start a new thread. Some people don't like to read through it all, but may still have the answer. A fresh topic is sometimes better.

Shawn

PS: Once the problem is resolved (please let it be the fuel pump! lol ), the moderator should be able to merge the two threads without any problem.

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

yep,those kits are often universal,for the sake of such a minimal cost,they include enough parts to cover a few different applications,you find this alot with carb kits too,the wheel part your talking about is for the front fuel inlet cover

Mike,

The front fuel inlet cover on my pump did not have a wheel type part. Is this supposed to be on all pumps, or only certain ones?

Thanks for all of your help.

SQ

 

[mikesea]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

certain ones ,yours might be an o-ring,different years,models,age,who knows,different manufacturers,I'm sue all you need will be in the package for ya.At least hope so after all you gone through so far.Keep us informed,helps us all learn.

 

[fireman57]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Shark fishing! That's pretty cool. The fuel pump diaphragms sometimes get a small pin hole(s) in them that cause problems that seem like they would be carb problems. Bet you can't wait until lunch. Good luck on the water and post back. Hope the family friend is recovering well.

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Shark fishing! That's pretty cool. The fuel pump diaphragms sometimes get a small pin hole(s) in them that cause problems that seem like they would be carb problems. Bet you can't wait until lunch. Good luck on the water and post back. Hope the family friend is recovering well.

Yea, the shark fishing is a blast!

The boat is for the 'off-season' or the local lake trips...the shark fishing from the beach is my #1 preference! Lately, it's been too cold to do much good...so I've been trying to fish out of the boat here locally. Can't do that if it wont run right!

I'll post up tomorrow when the fuel pump makes it in.

SQ

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Ok guys, got the fuel pump rebuilt. That was a breeze...

TIP TO ANYONE REBUILDING - run your screws through the back side of the pump to help line up the screw holes in your gaskets. Pull them out the back, and install them in the front one at a time making sure the diaphragm and gaskets are aligned.

I re-installed it, buttoned up the hoses, and gave it a test run on the hose.

It didn't act-up on me for the 10-15mins I had it idling on the hose. d

It also seems to idle a little smoother in general.

Heading to the lake after 5pm CST to give it a go, wish me luck!

8)

SQ

 

[dave208]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

The fuel pump works from the vacuum and pressure created by the engine as the piston moves up and down. One side of the diaphram is open to the engine crank case. The pulse created by the engine vibrates the diaphram which literally forces fuel on the other side of the diaphram into the carberator. A one way flapper valve allows the fuel to only go to the carbs and not back into the fuel line. This pump is about as basic as pumps get. If the flapper valve is bad the pump will work poorly at low speed. If the diaphram is bad, the pump will not work at all. In fact if a one way valve is in the fuel line, the pressure will build in the primer bulb, making it very hard to squeeze. I think you hit the nail on the head with your problem. Follow the instructions very carefully for your specific motor. You will have many extra parts with your kit. Make sure you have a good seal between the fuel pump and the engine block. Look very closely at the seal where the fuel line connects to the pump. Make certain you seal well at that point, and you should be good to go. Good Luck.

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Got it rebuilt and it seemed to idle fine! I did try to turn down the idle a bit before I went to the lake, and I think I turned it down a little too much, but I can fix that.

I also gained a few hundred RPM at the top end...not sure how or why, or if the cool air caused it...but it was turning 5500 if I wasn't careful, where I could only get 5000-5100 last week.

However, I think I may have found another problem :^ :/

After running it on the hose and posting on here yesterday, I went back out to ready the boat for the lake. I did a walk-around and noticed some 'sludge' built up on the inside of the prop. At first, it looked like gear oil and water mix, so I immediately assumed lower unit lube. There was a tiny bit of fishing line on the prob, but from what I could tell it didn't affect the lower unit at all because I opened the lower unit and drained it. All of the oil was still in there, no water in it at all from what I could tell...looked fine. It was a little dark, but nothing abnormal and no abnormal metal.

I'm wondering if oil can seep out, but water not be allowed back in?

Weird...I'm going to re-fill the lower unit and see if I lose any oil and/or find that sludge on the prop again. It may have just been buildup, but it looked excessive to me.

Thanks for the help guys - we've fixed my MISSING issue - Next!

SQ

 

[clemsonfor]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

That is unburnt gas/oil and water from the excessive ideling on the muffs in the yard. I have seen it before especially when my motor was running rich. This is probably what your seeing, since the oil was not milkey. Then again since you have not been submerged in warter while ideling in the yard if it is leaking it may not nessicarily let water back in. I am leaning more toward the first situation though.

-Nate

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Nate,

After running on the hose is when I saw it. However, it was a lot thicker than usual. If you've ever blown a headgasket on a 4 stroke automotive engine...the residue inside the prop looked just like the milkshake you get in your oil after a blown headgasket...

I took it to the lake, it ran great, and after a long 5000rpm run, I killed it and pulled the engine up and felt the outside of the lower unit. I figured if it was low on oil or leaking oil, I would see it, or feel the heat...it was barely warm.

So, I'm going to re-fill the LU and hope for the best.

Next up - thermostats, water cover gaskets, and head gasket change. Hopefully the corrosion wont prevent me from doing so.

SQ

 

[clemsonfor]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Thats what the stuff i'm talking about can look like!

-Nate

 

[ShawnQ]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

Well, that makes me feel a little better.

Hopefully the head gaskets will hold until I can fix them.

SQ

 

[mikesea]

Re: Intermittent Miss / Rough idle / Wont Rev - fuel related? UPDATED!!

SO is the engine now running OK.Did rebuilding the fuel pump solve your problem.Hope so.As for the lower unit questions,pull the prop off and make SURE all the fishing line is gone,it can cut your seas up.If your gear oil didn't have water thats good,your probably ok.You can pull the bottom plug every time after use(since you trailer)drain a bit into a glass and see if water is present.You don't need to drain alot out,just let it sit overnight so any water will settle to the bottom.If it stays OK don't worry about it.As for changing the hea gaskets ,WHY,is your compression down,or you just curious,i don't like to fix stuff unless it's broke,you may have a nice clean.freshwater run engine, but here in Fl.you can almost bet on bolts snapping off and stuff breaking while disassembling,just PROCEED with CAUTION.Hope all is now well.