Fuel Pump 7.4L

Dive Girl

Dive Girl

Active Member
Jul 15, 2009
239
Portland, OR
Boat Info
2003 460 Sea Ray Sundancer

2019 Zodiac Yachtline 360 tender / Yamaha 40hp
Engines
Cummings 6CTA 8.3 M4
Hi all! It's been a wonderful boating summer here in the PNW.

Last week, returning from a great weekend downtown Portland we "lost" our starboard engine. Such fun making the turn to get in the boat house! :smt100

Anyway, after analysis, it's the fuel pump. Does anyone have experience replacing this? Just wondering if we should tackle this ourselves or hire a mechanic. The guy we usually use couldn't get to it this week, and next week is out for him. Just don't want to miss this wonderful fall weather we're having! (Rains haven't begun in earnest)

Inboard 7.4L MPI Mercs 454 310HP

As always, I appreciate your suggestions and assistance!

Deb
 
If yours is like mine it's located under the motor mount and right next to the stringer. It's a true pain to get to, fuel spillage a big concern for me. Unless you are nimble, relatively small and young, which I am none of those things, then I'd hire it out!
 
No, it's a metal tube.

We can't seem to find it on the engine! Is it UNDER the engine?
 
We'll open up the hatch and look again. Thanks for the info Westie!

I'll let you know!
 
Update:
We found it! It's located behind an insulating panel and a bracket on the starboard side of the engine.
Due to it's location and the fact that gasoline is involved, we've decided to let a mechanic replace it.

Thanks for all of your help!

Deb
 
Update and help needed.
Fuel pump replaced. Yes, that was that issue. Now though, the engine starts but won't run below 2100 rpm.

ideas?
 
Did he pressure test the fuel pump and regulator after he installed the new pump? MPIs are sensitive to fuel pressure. If it seems that it is running out of gas below 2100 and stalls....I would start there first. Also, did he replace the fuel filters?

-John
 
No, haven't run those tests yet. Going to replace the fuel filter later today. It's looking like its time to call a pro. Drat!
 
While I don't have the exact specs in front of me the fuel pressure with the key on should be between 35-45 psi. When the engine is running at 2000 rpm the pressure gauge should be steady in that range +-3psi. If it is flucuating and the pump is new.....I'm betting on the regulator. Fortunately the filter and regulator change are simple fixes.

John
 
We'll get a gauge and check that. We're thinking the problem might also be that the pump isn't the same as the original. We gave the parts folks our serial number and engine model and they gave us the replacement pump for the original. It didn't fit the elbow that joins the pump to the gas cooler. They took it somewhere and had it modified to fit. Maybe the "hole" on the modified side is smaller so not letting gas to flow through.
 
The fuel pressure gauge screws on to a Schrader valve (think valve stem on tire) on the fuel rail (top of engine). The gauge should be able to read to 50psi and be designed for fuel. Uncap the Schrader valve cap, Screw on the Gauge hose. Some fuel will spill since the line is under pressure so make sure you have a rag under it.

Once attached, turn the key to the ON position....don't start it. When the key is turned on, the fuel pump is activated for 3-5 seconds and note the reading on the gauge. Start the engine the engine and observe the RPM and gauge reading. The readings between the engine ON and running on the fuel gauge should be very close. After it warms up, start pulling the throttles back and have someone watch the gauge. If it is the regulator or pump, the pressure will drop and the engine will stall. If it is another component, the pressure will stay steady even after the engine dies.

It is always good to have a fire extinguisher nearby and make sure the hose to schrader valve does not leak when the engine is running. Do not attempt to disconnect the hose unless the engine is off. Also it will leak again when you remove the hose.

-John
 
Last edited:
Dive Girl, nice to see you on here. The situation you're in sucks, but it's nice to see you on CSR again.
 
It's nice to be here. Have you had a good summer boating?

Hopefully it'll be fixed today! Fingers crossed!
 
OK, had a mechanic friend bring his computer down and plug it in to analyze the problem. It seems as though the issue is the MAP sensor. Should hopefully be an easy fix if we can find one.

But, now another issue! (It's a boat) We have a cracked manifold. Dandy... That'll get fixed this week. Luckily we have all the parts.

Fingers crossed, we're missing great fall boating weather! Thank goodness we've been able to at least play in the dinghy!

We're going to replace the spark plugs, can't find the Gap, or the manufacturer. Anyone know?

Thanks all!
 
OK, replace the MAP sensor. Still won't idle under 2100 RPM.

Fuel pressure way low! 8PSI. So, it's either a bad new fuel pump or the regulator. Drat, drat, drat! It looks like it's the last great weather weekend and we're tied up the next two weekends. Darn it! We'll still boat in the winter, but it's not the same.

I'm hearing the cash register go cha ching too.
 
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