Voltage Drop at Fuel Pump

[Dancrosswis]

What's Happened:

Started my M25 XPB today.  The fuel pump stopped clicking about 8 seconds into my glow plug routine.  The engine started normally, but then stopped dead (like I'd pulled the kill switch) after about a minute of operation.  No life from the fuel pump.   I pulled the positive feed to the pump to make sure it was getting power.  I only saw about 8 volts at the feed.  I checked the voltage at the powered post of the glow plug solenoid, and it showed full voltage of about 12.8 v.  I jumped a wire from the solenoid post to power the pump.  It ran, but was "arrhythmic", i.e. gave out a fast, muffled pulse, rather than the slower loud click I'm used to hearing.  I ran the pump for a total of about two minutes in short spurts, thinking I might need to bleed the fuel lines.  No response when I tried to start the engine.

What I've Done and Will Do:

I ordered a replacement Facet cube-style fuel pump.  I'm not certain the pump's the problem, but at only about $50 plus another $20 for two day shipping, it's a cheap first installment on a solution.  Thank You so much for the alternate fuel pump posts.  Westerbeke is selling their pump for $178.80 plus shipping.  I'll bench test the existing pump.  If it works on the bench, I'll keep it as a spare.  Tomorrow I'll try to trace down my voltage drop source.

My Questions:

• Am I right to assume that a drop to 8v at the fuel pump is not normal?
• Could the voltage drop have caused the fuel pump failure?
• Or, are the two just coincidental?
• Any recommendations for tracking down the voltage drop?
• Any other causes, issues I should be checking for?

As always, thanks in advance for any thoughts or suggestions,

Dan
1985 C34 Ennui Went
(repowered with M25 XPB)

[britinusa]

Did you test the voltage using the pump body as the ground?

If the voltage is only 8 volts when it's disconnected from the pump there are at least two options.
Bad Ground (-ve) or high line resistance (wrong gauge, wire damage, corroded terminals).

Establish a good ground (clean, solid connection)

Check the voltage at the engine panel end of the pump wire.

Paul

[KWKloeber]

Dan:

The XPB is a very different animal.  The fuel pump is powered by two sources:

1. Thru the solenoid switch next to the fuel pump (while preheating (and possibly cranking)).
2. Thru the low oil pressure switch (once oil pressure builds.)

The oil switch terminals are notorious for failure (vibration/movement from the STIFF ("Westerbeke's better idea," non-marine [automotive, non-tinned] wire) wire harness is transferred to the switch, and whammo.   Not IF, but WHEN.  I've posted about this many times and warned B-series engine owners to fix this ASAP.

Have you noticed any strange happenings w/ your oil alarm light or buzzer?
Do you have a seaward panel or the Wb panel?

I will have to look at the schematics and see if the solenoid could also cause low voltage -- it is wired very strangely with a permanent short to ground thru a resistor.   Huh, what?

In the long run, I suggest you do as Ron did and scrap that stupid "Westerbeke's better idea" system thru the oil switch.  if you want to bypass that "temporarily", I believe that you can tap into the alternator field excite wire (12v powered off the key switch) and power the fuel pump.  I will verify that when I can study the schematics.

Be cautious of preheating -- the solenoid is NOT a continuous duty and is a crappy cheap model Westerbeke used to save you a few bucks.  Being an intermittent duty switch, burn the preheat circuit too long and you will fry the solenoid coil.  I have posted about that a few times also and recommended that "B" owners replace that solenoid ASAP.

-ken

[Ron Hill]

Dan : BTW, the first year of C34 production was 1986.
Look in the Mainsheet tech notes and you'll find my M25XPB installation.  I modified the engine to match the boats wiring and fuel setup instead of the other way around --  MUCH simpler!!

A few thoughts

[Stu Jackson]

>>>>>>>>>>>>>>>>

In the long run, I suggest you do as Ron did and scrap that stupid "Westerbeke's better idea" system thru the oil switch.  if you want to bypass that "temporarily", I believe that you can tap into the alternator field excite wire (12v powered off the key switch) and power the fuel pump.  I will verify that when I can study the schematics.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

Ken's right.  IIRC, there's a post in the Critical Upgrades, concerning "Hard Starting" and the glow plug/oil pressure stuff (http://c34.org/bbs/index.php/topic,5078.msg41829.html#msg41829)  that discusses this very issue and provides a link to a much longer discussion about this very issue that is not specifically about the XPB either - it pertains to other engines, like the M35s.

I agree with Ken, Wb's idea leaves some room for improvement.  Like Ron did his: the old way! 

[Dancrosswis]

I ran a number of multi-meter tests on Saturday to track down my voltage drop, came to an initial conclusion, and proved that wrong.   First, the test results.

Ground.  I first checked the condition of the preheat solenoid ground (the metal bracket the solenoid is attached to), by measuring the voltage at the bracket and at my battery bank negative.  No voltage reading, so I'm assuming my ground is good.

Measurements at Preheat Solenoid Terminals.  I know the solenoid on my motor is not original and do not know whether it differs from the original.  I don't know the make of my current solenoid.  Napa ST81 looks identical to my solenoid.  I don't know whether it's rated for continuous duty.

Here are the results of a number of tests:

DP Power	Key Switch	Preheat Bttn	S Terminal	I Terminal
On	Off	Off	0.00	0.11
On	On	Off	0.01	4.78
On	On	On	10.8	11.9

The third test was done with wire at the S terminal attached, i.e., the solenoid was operating.

After running these tests, I (wrongly) concluded I must have a defective solenoid.   With the pre-heat (glo-plug) button off (i.e., not pushed), there should be no voltage at the S terminal, which the meter bore out, but then why is there voltage at the I terminal?  And, with the pre-heat button on (pushed), there's more voltage at the I terminal than at the S terminal.  Where is the extra voltage coming from?  I surmised that the solenoid must be leaking voltage from the "power-in" post to the I terminal.  I replaced the solenoid with a new NAPA ST81.  Retested.  Same results.  I still don't know where the extra voltage is coming from.  I realize that when the engine is running voltage will be back fed to the I terminal from the alternator through the oil pressure switch.  Maybe something else is back feeding to the I terminal when the key switch is turned on?

Measurements at Instrument Panel.  I measured full system voltage at the B terminal of the instrument panel key switch.  My testing at the instrument panel didn't get any further.   I don't know what make instrument panel I have.  I believe it's the boat's original.  Photo attached.

Oil Switch Terminal.  I haven't checked this, yet.  I've just begun to read the prior posts about oil switch problems.  I'll settle on a strategy after I complete that reading.

Oil Alarm Light/Buzzer.  I'm not sure my alarm lights work.  Gotta check that.  The buzzer goes off as soon as I turn the key switch on and before the engine fires.  I assume this is correct.  There's been no change in the buzzer's operation.

Engine Wiring Diagram.  My wiring harness at the preheat solenoid matches the wire colors shown in Wiring Diagram #39144 (page 94 of January 2001 M25 XPB Service Manual).  My instrument panel doesn't match either the Admiral or Captain panels of the wiring diagram.  I drew a wiring diagram of my panel, if that helps in deciphering this gremlin.

My Current Plan.  The new Facet pump will arrive Wednesday.  I'll install it and hope that's the short term fix.

Production Start.  Yea!  My boat's one year younger!  Sorry.  I got sloppy with my post.

[KWKloeber]

You have the Seaward Panel, not the Westerbeke/Universal.

[KWKloeber]

Dan

You need to use the schematics on pg 93, 94.
UPDATED:  With the caveat that the preheat solenoid is triggered by the glow plug PB switch, not Key Switch "S" position.

I would check continuity/resistance by an ohm reading between, say, the case of what you are measuring (eg, solenoid) and a good ground (eg engine block).  understand that at rest the r4sistance MAY be different than with current closing.  LOW current flow shouldn't affect that.

I'll have to study the schematic, but IIRC the Wb wiring back feeds some voltage to keep the alarm from sounding in some condition.  That's just in the back of my mind (CRS) so do not take that to the bank!

BTW, the 10a breaker bolted to the solenoid is non ABYC compliant - auto-reset breakers are verboten. 
As well, the 20a manual reset breaker would need to be 7" from the starter, so it's also non-compliant. 
Both are just Westerbeke's "attention to detail."

-ken

[KWKloeber]

Dan

Re: your tests and the low voltage at the solenoid.  You have to trace out exactly what's "hot" in each scenario.

With no oil pressure (key on, not running) below is hot.  See the short to ground (thru a power resistor) that I mentioned in my first post below?  That will be bleeding voltage off the circuit.  Plus the fact that the voltage at "I" is back-feed thru the alarm buzzer, to the solenoid.



-ken

[KWKloeber]

Dan

And when you preheat, it's not a matter of where the additional voltage is "coming from", it's "where is the voltage going to."  You are powering the "S" terminal, which energizes the coil inside the solenoid (holding the switch closed) and that will draw down the V+ @ "S."

Meanwhile, full voltage is supplied elsewhere, so (near) full battery V+ is seen @ "I". 

Notice that full voltage is provided to the lift pump (thus providing fuel even tho there's no oil pressure.) 
When there is full voltage to the pump (either during preheat or running w/ oil pressure) the backside of the alarm also receives 12v, so it silences the buzzer.

Soapbox: IMHO it's dum using a power pig like a starter solenoid meant for 150 amps, to fire 18 amps of glow plugs.  DUH. It should be a simple, reliable, 30a (40a for a 35B) continuous-duty (headlight) relay  (that are dirt cheap at any auto parts,) and that are a simple push-in replacement (pops into a standardized socket, below.)

More soapbox that many don't care to hear: The issue of your solenoid points out the folly of adding a preheat solenoid to the non-"B" engines.  It's totally unnecessary and only complicates the electrical system (read: adding unneeded components and so more failure points.)  For "faster starts"? i.e., reducing the preheat time from, say, 30 secs to 10 secs.  Really? REALLY?  And then sit at the dock for what, 10 minutes warming up the engine and preparing to shove off?  Maybe others feel shaving 10.50 minutes down to a more palatable 10.17 minutes, offsets the added chance of failure.  But IMHO, KISS baby. IIWMB-engine, that system would be ripped out the first chance I had.





http://www.c34.org/wiki/index.php?title=Faster%2C_More_Efficient_Glow_Plug_Heating_with_a_Solenoid#USING_A_RELAY_TO_FIRE_THE_GLOW_PLUGS:

[Stu Jackson]

Further to my earlier post Reply #4, this is what I was referring to in the Critical Upgrades topic thread:

In 2007 we had discussed this in a very looong thread:  Hard Starting/ Possible glow plug problem?? M35 Engines & Fuel Pump Wiring

http://c34.org/bbs/index.php/topic,3347.45.html

Reply #54 on page 4 of that topic begins to discuss the wiring to the fuel pump, how it works, issues with bleeding...

I just looked at it, try starting at the top of the page, Reply #52 is longer and gets into the nuts&bolts.

That thread discusses the very wiring diagrams Ken has so helpfully posted.

One VERY IMPORTANT take away from that discussion is that there are two wiring diagrams that purport to show the same thing.  IIRC, they may well be the same number diagram, 200360, that Ken posted.  [It IS, see Reply #47 in the link.]  They are both in the manual.  One is a schematic, the other shows physical relationships and connections.  I discussed the differences between these SAME NUMBERED DIAGRAMS  in the link in this post.  It is CRITICAL when looking at them that you understand the differences, in addition to Ken's observations. 

[Dancrosswis]

Gentlemen,

My new fuel pump will be Amazoned to my doorstep tomorrow.  I'll dive deep into your recommended readings in the morning before I head back to the boat.  Just wanted to make a few quick observations.

1.  I'm having as much fun deciphering your acronyms as I am tracing the wiring diagrams.  I'm not being sarcastic; they're both fun.

2.  I don't appear to have the 1OA circuit breaker or resistor to ground at my solenoid I terminal.  Should I worry about that?  Could it be buried somewhere else in the harness?  Should I install both?

3.  My start button is powered from the I terminal of my key switch, not from my preheat button.  Am I right that I can disengage the preheat button and then press my start button-and avoid powering the glo-plugs and the starter at the same time?

4.  I'm continually amazed at the depth of knowledge available through this association.

I'll send an update after my next boat visit.

[KWKloeber]

1.  I'm having as much fun deciphering your acronyms as I am tracing the wiring diagrams.

Dan

1. Stay with us, occasionally they get R rated when the topic gets hot enough.
2. In his book, James Klapper equates testifying before Congress as being as much fun as a) "Oral Surgery" and B) "trying to fold a fitted sheet."

Surely schematics are up there with those?

[KWKloeber]

Reply #54 on page 4 of that topic begins to discuss the wiring to the fuel pump, how it works, issues with bleeding...

I just looked at it, try starting at the top of the page, Reply #52 is longer and gets into the nuts&bolts.

One VERY IMPORTANT take away from that discussion is that there are two wiring diagrams that purport to show the same thing. 

Stu

I didn't read the entire thread (which was before my time) but did skim some parts you noted. 

I noticed the tête-à-tête about the schematic vs the diagram.  I pulled mine from the service (technical) manual -- not sure where they were referenced from that thread.  No matter anyway, they are the same.

I thought after reading your comment about the circuit breaker and resistor locations, you might be onto something.  So, I traced out the circuit paths from the "I" terminal to each component that is electrically connected to it.  Ipso, the:
* Circuit breaker
* Resistor to ground
* Oil switch
* Alarm "P" terminal
* Lift pump positive

L&BH, the two are identical, well functionally, of course not visually.  I colored each circuit path differently to each component after the "I" terminal.  Where one wire or schematic leg handles multiple component paths, I indicate multiple colors.

At least to my eye, the diagram and schematic depict the identical electrical paths, albeit they are visually different.  Review those below and see if you agree, or can you see where something differs?

-k

[KWKloeber]

2.  I don't appear to have the 1OA circuit breaker or resistor to ground at my solenoid I terminal.  Should I worry about that?  Could it be buried somewhere else in the harness?  Should I install both?

3.  My start button is powered from the I terminal of my key switch, not from my preheat button.  Am I right that I can disengage the preheat button and then press my start button-and avoid powering the glo-plugs and the starter at the same time?

Dan

2a)
The 10a CB is there to protect the harness down circuit from "I".  Unlike gravity, it's a good idea but is not a law. 14awg wire in an engine space can handle 30 amps (and the manual CB *should* trip if there is a short.)   So theoretically at least, the 10a CB isn't needed.  Since it's non-compliant anyway, you might want to eliminate it or replace the CB with a weathertight AGC fuse holder.  Those type auto-reset CBs do go bad - I had to replace one when I redid an M25XPB harness (with tinned MARINE, not bare copper AUTOMOTIVE WIRE) a couple yrs ago.  The same guy, BTW, who burned up his solenoid by glow-plugging too long.  If he hadn't already replaced his solenoid, I instead would have wired his harness with the aforementioned headlight relay socket.

2b)
I don't see how the alarm circuit would work as intended if the resistor isn't in the circuit.  BUT, I would have to stuty that a little before passing that off as gospel.  It's just a dumb set up overall -- what engineering brainiac would think it's a good idea to intentionally wire in a direct short to ground thru a resistor.  Only Westerbeke!  Again, building in more failure points than is absolutely necessary is not only "not a great idea," it's a "really bad idea" on a boat.

3)
Given the parallel feed to the start and preheat buttons (IIRC there's a 10 awg jumper from "I" to the preheat button v+, then to the start button v+,) yes, you can physically do either/or, or both.  YBYC.