Rewiring Fuel Pump at Ignition Switch

Dave Spencer · June 29, 2011, 05:42:05 PM

Hi Folks,
I had to change filters and bleed my fuel system at sea last weekend... the result of some old fuel in our new boat that I failed to properly consider before heading out. The worst part of the job was keeping the engine fuel pump running. Our 1994 C34 #1279 with an M35AC has the fuel pump wired in the "momentary" position on the keyed ignition switch meaning that to get the fuel pump to help with the bleeding, the key had to be held in the momentary position which also powered the glow plugs.

I had the Admiral hold the key for 5 or 10 seconds at a time while I inspected the air coming out the bleed screw on the secondary filter until it ran clear. Eventually, we had success but surely it isn't right to have the fuel pump powered in the momentary position. Should it not starting ticking away when the switch is in the "ignition" position? I thought I saw something about this change somewhere on the website but my search parameters haven't come up with anything.

Any help on this would be appreciated. Otherwise, I'll fiddle with it this weekend and document my results for the group.

Fair winds to all on this wonderful long weekend with Canadians getting Friday off and our friends in the United States getting Monday. I'm taking both days!

Stu Jackson · June 29, 2011, 05:52:13 PM

Dave, you might be interested in this: http://c34.org/bbs/index.php/topic,3347.45.html

I'd added it as a Link on the "Electrical 101" thread, and I just added it to "Critical Upgrades," too, for easier finding, since Critical Upgrades is a sticky.

Any questions, let me know.

Ron Hill · June 29, 2011, 06:23:49 PM

David : The electrical fuel pump on the M35AC wiring diagram shows that it could be to the new type fuel pump (square) on the back of the engine or the old cylindrical pump under the head sink (dashed line).
The key to where it gets wired in the ignition switch - is how many contacts are on the oil pressure switch.
If you have 2 contacts on the oil pressure switch then the fuel pump gets wired to the same spring loaded pole (I) as the glow plugs. If you have only one contact oil pressure switch then the fuel pump gets wired into the (C) continuous ON pole of the ignition switch.

As I've mentioned before the C34 fuel tank is higher than the engine and should gravity feed to the injection pump. Your year boat should NOT have a screen in the pickup tube, but it may be worth checking. If your engine will not run without a fuel pump and you have over 1/2 full fuel tank there's a restriction in you fuel lines - somewhere?

Everyone seems to forget (or never knew) that in the top of your Racor fuel filter there is a "finger pump"!!!!
You can unscrew that cap on the top and it will pop up. Your finger will get tired, but you can bleed the system and keep the engine running in an emergency.
A few thoughts

Dave Spencer · June 29, 2011, 06:41:57 PM

Thanks for the quick response Stu. The link to the post is indeed long and will require quite a bit of study. Ideally, I was hoping that I would find a wiring diagram showing what needs to be changed to get the fuel pump running in the "run" mode on the key switch. I certainly agree with your post #59 from the link you provided above that the "feature" of cutting the fuel pump if the engine oil pressure is low is not that great an idea. I am perfectly willing to bypass this feature and rely on the the low pressure visual and audible alarm in the unlikely event that I lose oil pressure. In my experience, losing cooling water is far more likely.

One of my friends with a CS36T and a Westerbeke engine has added a bleeding booster pump to his fuel system which is something from NAPA (or somewhere) that allows full fuel flow through it when not energized but when powered, sucks fuel through the RACOR and forces fuel through the rest of the system making bleeding a 10 minute job with no mess. This would be very similar to the system that worked well for me in my previous boat, as CS27 with a Yanmar YSB8 engine. I may give this a shot if I can't easily change the function of the engine mounted electric fuel pump.

Ron,
As I was writing, you posted your comments. Thank you... very helpful. I have the round pump. and evidently a 2 contact oil pressure switch.
I figured out the finger pump on the RACOR. Neat but slow. I plan to pull the fuel tank this weekend and do a thorough cleaning job on it as documented in the tech wiki. Unfortunately, the tank is about 3/4 full so I have 4 20 litre containers in the car ready to capture the fuel I pump out. I plan to "polish" the fuel by pumping is through the RACOR into the containers... as long as I can get the pump to work... I may disconnect the glow plugs at the ignition switch temporarily for this job. I also have all new fuel hose and 8 litres of acetone to clean the tank. I'll check for the screen and make sure it is removed.

Any other thoughts?

Stu Jackson · June 29, 2011, 08:18:53 PM

Dave, save some effort and re-read my link. There may be a way to jumper the fuel pump. You may not even have to mess with the cockpit panel switch. I think Ron may have explained it in that thread. KISS.

No one I know has a wiring diagram as to how to jumper it, but that's simple. The wiring diagram of what you DO have is discussed in the link and is available in the wiki. Those were the two that I said did not agree with each other.

Stu Jackson · June 30, 2011, 09:16:22 AM

Dave, I just went back and re-read that thread again.

My Reply #54, in part, said:

"Suggestions: If you agree with that, then you really don't have to do anything with the wiring to the cockpit control panel, assuming you've resolved the wiring diagram discrepancies noted in my item 6 above: do two things all "underneath" and not in the stanchion to the cockpit panel -- disconnect the wire from the solenoid output to the fuel pump [correction](per page 25 wiring diagram which shows two wires into the pump vs. page 26 which shows only one) and jumper the oil pressure switch so that the pump always runs when the keyswitch is ON (the oil pressure switch will still provide an alarm)."

That's the "simple" change in wiring I suggested, which Ron followed up on.

John Sheehan also mentioned it in Reply #61 on page 5. Also see Reply #63 on page 5.

Dave Spencer · June 30, 2011, 04:02:47 PM

Thanks very much Stu. I'm heading up to the boat on tomorrow and will do exactly as you suggest. If I can, I'll document it with pictures to help others who may run into the same problem. My only potential issue is that I only have the old M35 manual and the new M35B manual. I haven't found a manual yet for the M35A that describes my cockpit panel configuration and wiring. I'm sure I'll figure it out.

Stu Jackson · June 30, 2011, 04:52:26 PM

Dave, one other thought: These "newfangled" engines are supposed to be self bleeding, right? So, if I put aside my tiny little mind's limited worldview, restricted to my ancient M25 prehistoric engine, shouldn't your engine be self bleeding? If so, wouldn't simply turning on the glow plugs for a short time turn on the fuel pump and bleed the engine all by itself without having to "work" the knurled knob? If you put fuel or injector cleaner in the Racor, that should eliminate most of the air.

Only "issue" comes up when you change the secondary engine mounted filter and need to pop that small nut to get the air out, but maybe the glow plug thingie would work then, too. Aha! Seems you've "been there - done that!" Oh well...

Downside, of course, is the electrical load in having the glow plugs ON while all this is happening. Probably be at a dock plugged in, but...

I guess the downside there would be you'd need two people to do that - one below and one at the panel/key switch. That's why I put in my fuel pump SHUTOFF toggle switch, so I could leave my key switch ON, and shut off the fuel pump when doing the secondary filter. (Reply #7: http://c34.org/bbs/index.php/topic,5558.0.html)

Just trying to look at it a different way than my referenced link.

That said, the very last post in the Hard Starting... thread kinda covers that, don'tcha think?

Happy Canada Day and good luck tomorrow.

Stu Jackson · June 30, 2011, 05:00:00 PM

Quote from: Dave Spencer on June 30, 2011, 04:02:47 PM
only potential issue is that I only have the old M35 manual and the new M35B manual. I haven't found a manual yet for the M35A that describes my cockpit panel configuration and wiring.

If the manuals on our site don't have it, have you tried www.marinedieseldirect.com ?

Dave Spencer · June 30, 2011, 05:37:59 PM

Thanks for the link Stu. I did try Marine Diesel Direct and almost anything else Google could throw at me. They list the M35 and M35B but not the M35A. The PO had excellent documentation for everything on the boat but the manual is for the M35, not the M35A. Our boat is a 1994 model built in late 1993. I see the M35A was only in production from 1993 to 1996 so maybe the manual wasn't developed yet when my boat was built. I suspect the differences are subtle in most circumstances but they're important in this case. I'll be working in the sunshine with my multimeter to try to figure this out... strangely, this is my idea of fun.

Stu Jackson · June 30, 2011, 06:19:03 PM

Ron has suggested many times that Joe Joyce at Westerbeke is a very good resource. Might want to do a search here for his name, Ron usually posted his phone # (it actually may be in that first link). Try him early tomorrow before the holiday(s) begin.

Ron Hill · June 30, 2011, 07:51:28 PM

David : We are beating this thread to death! Here's some history as I remember it :

The first M35(30hp) in a C34 was back in (I believe) 1990 as an option. The Universal Engine was sold(from Oshkosh WI) to Westerbeke right around that time!! You can tell which is which by the Oshkosh metallic bronze or the silver blue Westerbeke paint. The original M35 engines thru at least hull #1244 had a bleed knob on that engine with a double contact on the oil pressure switch. On the faucet round fuel pump the case is the ground. I'll look at my engine tomorrow (it's 10:27PM here on the boat and I'm getting tired) and tell you where the square pump wires go.

I don't believe there is any better wiring diagrams than what you got with the boat. Joe Joyce is at Ex234 (508)263-6700.

If you want to rewire your fuel pump that is another topic. When I installed my new Westerbeke Universal engine I removed the entire wiring harness and made the new engine wiring to match the boat instead of the other way around. I replaced the double contact oil pressure switch with a single pole switch. By passed the square fuel pump and used the my cylindrical fuel pump. I also by passed the circuit breaker to that mess and wired in a 20amp fuse to the starter solenoid. Put in heavier wiring for the glow plugs .

Everything works fine and is much simpler!! I'll look at that fuel pump wiring tomorrow.

Bottom line still is that in a C34 the engine ANY ENGINE should run without a fuel pump (and gravity feed) because the fuel tank is higher than the engine. If you can change your Racor filter with out shutting off the fuel - then you've got a problem!! The gravity should syphon fuel all over the place!!
Hope this helps.

Ron Hill · July 01, 2011, 08:46:55 AM

David : I looked at my square pump. There is a red and a black(painted silver blue) coming out of the pump body. The red wire connects to circuit breaker and the oil pressure switch according to the wiring diagram. It's interesting that the black wire(-) is grounded to the bolt at holds the pump to the engine, so the metal outside body is in essence also grounded.

The wiring diagram shows the red wire splitting into 2 purple wires to the oil switch and circuit breaker from the square fuel pump. Don't have my harness handy (in the attic) so I can't confirm the diagram.
Hope this helps.