Dies Suddenly while Cruising

[JoDo]

So I was able to get up there today and pressure test the fuel pump and it measured around 5.5 psi. Below the range Mike stated so I put the new one on. Problem is the fuel inlet and outlet are in different positions than the original so my steel fitted line won't work. Actually the outlet to carb was pointed at the block so I couldn't even get that line on. I rotated the center and lower body portion together so I could get the carb line on but that still left the inlet in a different spot. If I could rotate the lower body alone 180 deg that would have solved it but because of the valve orientation in that lower body it did not appear to me that I could rotate it and still have it work correctly. So I will get flexible fuel line and go back up tomorrow. Either way I'm feeling pretty good that this solves my problem. The low reading and the poor, leathery condition of the old diaphragm upon inspection tells me this pump needed replacement. I'll update tomorrow evening.

[speedysprocket]

Should be able to unscrew the fuel pump body and reclock it to match your old one.

[mmwjr]

Where did you get the new pump?

You should be able to get one that does not require re plumbing the fuel lines.

[JoDo]

I got it at NAPA, it is a marine pump with a Mercruiser part number. I didn't try a marine shop since NAPA is so close and they had it. Before I installed, I called them to make sure they gave me the correct one and he said he did.

The lower body can be rotated 180 but it has two valves in it that appear to be set in opposite flow directions from eachother. Is my assumption correct that I cannot simply rotate it? The diaphragm between the two is open on one side and solid on the other. This would change which valve is on the open side.

[JoDo]

The other thing is, I see no inline fuel filter anywhere. Installing a new flexible line would also let me easily put a fuel filter on.

[speedysprocket]

Is this what you got? If all those little screw are on the same side of the flange, you can take them out and rotate the pump inlet/outlet.

[ss3964spd]

5.5 PSI output is still good, especially for a QJ since they don't like high pressure, and even more so if it has a high flow needle and seat assembly. The real test is when the engine dies, and before attempting to re-start, remove the flame arrestor, look down into the primaries, and operate the throttle. If you see two jets of fuel being discharged from the accel pump boosters when you move the throttle it means there is still fuel in the carb, which further means fuel delivery isn't the issue.

Nevertheless, if the old pump is original certainly won't hurt to replace it.

The filter is located behind that large nut/fitting on the carb where the feed line attaches. If you do add an external filter be certain not to use a plastic or glass filter, metal only, and be sure to properly support any flexible line.

[JoDo]

That is the orientation of the original. The new one has the inlet and outlet different. The upper (out to carb) was rotated about 20 deg to the right and the lower exactly 180. Now I could take out the little phillips screws and rotate that whole assembly no problem. My issue is if I separate the two bodies and rotate from eachother it will not work because there are two valve/diaphragms in there that are opposite directions.

I'll tell you what, every google pic I pulled up has shows the correct orientation. I'm starting to get pretty pi$$ed at Napa. I'm going to pull that thing and take it back. It's been installed but no fuel has ever gone through it. And, I called and double checked with the guy before I did anything. I'll go in to Spokane and get the correct one.

[JoDo]

Originally Posted by ss3964spd

5.5 PSI output is still good, especially for a QJ since they don't like high pressure, and even more so if it has a high flow needle and seat assembly. The real test is when the engine dies, and before attempting to re-start, remove the flame arrestor, look down into the primaries, and operate the throttle. If you see two jets of fuel being discharged from the accel pump boosters when you move the throttle it means there is still fuel in the carb, which further means fuel delivery isn't the issue.

That was the first thing I did out on the lake and I got fuel. However the problem is only at high RPM so I didn't take that as a sure sign. The only electrical thing left is the Thunderbolt IV. Would that fail only at high RPM? Or at least only intermittently?

[ss3964spd]

I went back and re-read your 1st post. Motoring along at 3K then just dead, no sputtering etc. Checked for fuel which was there. Ran it again and same symptom. But then in post 11 there are new symptoms.

In my experience engines with mechanical pumps and carbs tend to cough, sputter or gradually lose power from a fuel delivery issue. Certainly a tired mechanical FP can deliver enough fuel at low RPM's but not at sustained higher RPM's, but the accompanying symptom would be coughing, sputtering, or decreasing power as the A/F ratio starts to go lean so IMO the symptoms don't fit for a fuel delivery issue.

As Mike suggested in one of his posts the ignition module can indeed get hot and shut down the ignition. Once it cools off a bit it's fine - until it gets hot again. Basically the heat is causing an open circuit within the module. Once that happens it probably takes less and less to make it happen again. I'd guess vibration also plays a roll over time (the ECM on our boats' engine has rubber mounts).

Your initial symptom just doesn't sound fuel related to me.

Dan

[ss3964spd]

Some links in case you've not found them yet.

http://www.boatfix.com/merc/bullet/83/83_24.pdf

http://www.marinemechanic.com/merc/d...ents_EN_14.pdf

[JoDo]

Well the cap and rotor are good the coil is good the wires are good so that just leaves ignition module and/or ignition amplifier according to that service bulletins. Now is the ignition amplifier a replaceable part? If so is it a likely culprit?

Sent from my GT-N8013 using Tapatalk

[mmwjr]

Originally Posted by JoDo

Well the cap and rotor are good the coil is good the wires are good so that just leaves ignition module and/or ignition amplifier according to that service bulletins. Now is the ignition amplifier a replaceable part? If so is it a likely culprit?

Sent from my GT-N8013 using Tapatalk

From talking with fellow boaters and their issue the ignition sensor in the distributor is much more common than the amplifier.

[JoDo]

Just got back from the boat. I took off the fuel pump so I can return it. While there I checked the little module inside the distributor. It looks to be in rusty shape. Could this be my problem?

[mmwjr]

Originally Posted by JoDo

Just got back from the boat. I took off the fuel pump so I can return it. While there I checked the little module inside the distributor. It looks to be in rusty shape. Could this be my problem?

These are know for thermal interminint issues.

[JoDo]

Thanks Mike, could you define "Thermal Intermittent Issues" for a layman? Does that simply mean when it gets hot is fails sometimes?

[mmwjr]

Originally Posted by JoDo

Thanks Mike, could you define "Thermal Intermittent Issues" for a layman? Does that simply mean when it gets hot is fails sometimes?

You got it.

[JoDo]

When I search for this part I keep getting a different style. Is this a replacement for what I have?

[mmwjr]

I believe so as the one you have is no longer made.

The new one will come with instructions on how to install it.

[JoDo]

Originally Posted by mmwjr

I believe so as the one you have is no longer made.

The new one will come with instructions on how to install it.

No instructions came with it. Google is proving fruitless. Anybody have a link?