AD21 fuel pressure

[Plum76]

Anybody know what the recommendation is for fuel pressure on an AD21? My boat has been retrofitted with an electric pump and I’m thinking it would be handy to have a fuel pressure gauge in the system somewhere, maybe even two, pre and post filter?

Thanks.

Jason

[dkirsop]

There is no recommendation for the fuel feed delivery pressure in the shop manual for the AD21. They simply state that it is an AC Diaphragm Pump and that the maximum suction lift should not exceed 5 feet. The fuel consumption is so low that I am not convinced there would be any benefit from installing pressure gauges, just change the filters at the recommended hour rating or every 2 years whichever comes first. By the time you registered a pressure drop it would likely be well past the recommended replacement period.

When I bought my boat the PO had installed an electric pump but had left the diaphragm pump installed. He had made a cover plate for where the diaphragm pump goes but had not got around to installing it. I went to install it and found that the electric pump did not work. Neither did the spare electric fuel pump that he carried on board. The boat had been running solely on the diaphragm, pump! I decided the original pump system was more reliable, rebuilt the diaphragm pump, and have continued to use it. The two electric pumps were used for ballast in my garbage can.

[honza]

I have never seen a pressure gauge in a delivery system for a diesel of this vintage and would consider it an unnecessary complication, and its hook-up as potential place for air leaks. On my leaky AD21, before the repowering, I had both pumps installed inline and it worked ok, but it is not needed - if the engine has not been busted by the POs.

[Bob Noodat]

1. Care should be taken with older systems in matching pressures. Most modern electric pumps would pump at higher pressures than a diaphragm pump.
2. If your fuel line fails and your engine dies, a mechanical pump stops. An electric pump, on the other hand, keeps going, giving you an additional emergency to deal with.

[Plum76]

Yeah, I don’t know the reason why the PO installed an electric unit, but that’s what I’m stuck with for now. Also installed is a return line with a valve so that I can ‘bleed off’ pressure and not over feed the motor, but that adjustment is by feel, would be nice to have a gauge to see what actual pressure is. I’m replacing fuel lines this fall anyway, as part of my diesel tank remove/clean/reseal, so putting a tee fitting inline to take a small gauge isn’t much additional work, just need to know what range I need.

The only reference I’ve seen to fuel pressure was something like 165bar for the injectors, but that doesn’t seem right, way too high, maybe 1.65 bar (~23-24psi)?

Agree on the pump running past the engine dying concern, my pump is on it’s own breaker and tied to my ignition relay, so has to be switched on and only powered when ignition is on, so have some safeguard against running for no reason..

Jason

[Bob Noodat]

There is some information available on the AD21.

The suction lift of the AD21 feed pump is 5 feet. To convert lift to psi, divide by 2.31. Obviously this is about 2psi. This low number doesn't surprise me for a diaphragm pump, in fact I would expect it.

An electric fuel pump may be designed to have a return line or not. Depends on manufacturer's installation recommendations. The valve fitted in your system seems like an attempt to find a solution to a problem created by fitting an inappropriate pump.

I think you should return it to stock.

P. 24 of this has specs:
https://marinedieselbasics.com/wp-conte ... ctions.pdf

[Plum76]

Thanks for that reference, returning to stock has occurred to me, but not quite an option for the remainder of this season, we have about a month left or so, and I would need to troubleshoot/replace the mechanical pump.

I’m still a bit unclear on pump output. The suction head you refer to would typically be the amount of head the pump can draw on the inlet side, so the pump could (in theory) operate above the fuel level of the tank and still pull fuel. I’m assuming this is to overcome any frictional losses due to lines/filters, etc.

Injection pressure is listed at 165 bar again, and I can’t see how either pump (stock mechanical or electric retrofit) is putting out anywhere close to that. Assume actual pump output is low double digits or single digit psi, but unclear.

Jason

[Bob Noodat]

The diesel injector pump is putting out the very high pressure. Quite separate from the fuel pump, which is just feeding sufficient fuel flow to the injector pump.

This might be useful:
https://albinmotor.nl/en/fuel-system-diesel/

[WillieC]

Surely Stefan at Albinmotor has a brand new mechanical pump just waiting for you. We have the newer Volvo Penta engine the lift pump on which continually soiled my shiny engine compartment. I tried taking it apart and looking for a rebuild kit which cost about as much as a replacement Beta38 engine, installed. A good suggestion from another AOGer led me to ASAP Supplies in the UK. I put in a new mechanical lift pump, in line with the cheapo electric pulse lift pump which is used for bleeding, and all is well. Spend the big bucks on this one. A mechanical lift pump will last decades, if used.

(Edit: It's Stefan, not Stephan. My apologies.)

[Bob Noodat]

The injector pump is #1 in this diagram: (whoops! now corrected)

Screenshot_20200826-121356.jpg

Found here:
https://albinmotor.nl/wp-content/upload ... _EN_SE.pdf

From here:
https://albinmotor.nl/en/downloads/

[Plum76]

I think you wanted the prior image, I think #1 in your attachment is actually the starter setup, but #1 in the prior image in the catalog is the fuel system/injector pump.

Point taken on getting back to stock, will be looking at that prior to next year. For the remainder of this year, I'm hoping to get through with what I have, not sure where the previous owner's issues lay and why they went to electric, but here we are. Just so I'm clearly describing things, PO had replaced mechanical lift pump to filter with an electric unit, otherwise I think i'm pretty stock.

The valve they retrofitted lies on what I believe is the stock return line to the tank, on the 'downstream' side of the fuel filter mounted on the block, presumably to deal with an overpressure or overfeeding issue, typically it's just barely open, and it's only a 90 degree turn ball valve, so not doing a whole lot of bypassing that I can determine. Again, the system I inherited.

What's sparking this is a stalling issue that just started the other day, about 15 minutes off the mooring. Motor stalled (like it was running short of fuel) and then wouldn't restart. Not something i've had before, so I'm trying to sort that out. On my list is to change the fuel filter (I bled my fuel rail and checked my fuel/water separator on the boat) and check that my electric pump is still pumping (I can hear it running). I only have ~50 hours on the fuel filter (changed last fall), so that's more of a guess and would be done later this fall anyway. Tank is running 5/8 to 3/4 full, and I haven't had to put any questionable fuel in, mostly from the pump via 5 gallon cans, one instance from a reputable fuel dock, so I don't think bad fuel. Have been using a diesel additive when adding fuel as well, to prevent fouling.

Dunno, trying to better understand what I'm sorting out. Have a spare electric fuel pump as well, that I can swap out if that appears to be the issue, but as long as it's pumping anything, seems like that's not really the issue..

Thanks for input, very much appreciate it.

Jason

The injector pump is #1 in this diagram:

20200826_101327.jpg

Found here:
https://albinmotor.nl/wp-content/upload ... _EN_SE.pdf

From here:
https://albinmotor.nl/en/downloads/

[Plum76]

I just received a shipment from Stephan, he's a great help with sorting out original parts. I'm sure he can provide a replacement diaphram pump (if they're available, will check).

JP

Surely Stephan at Albinmotor has a brand new mechanical pump just waiting for you. We have the newer Volvo Penta engine the lift pump on which continually soiled my shiny engine compartment. I tried taking it apart and looking for a rebuild kit which cost about as much as a replacement Beta38 engine, installed. A good suggestion from another AOGer led me to ASAP Supplies in the UK. I put in a new mechanical lift pump, in line with the cheapo electric pulse lift pump which is used for bleeding, and all is well. Spend the big bucks on this one. A mechanical lift pump will last decades, if used.

[Plum76]

I think this would be my replacement mechanical fuel feeder pump:

https://albinmotor.se/komplett-prislist ... ump-ad2-21

Jason

[WillieC]

$68 USD! Buy two and sell one to Mr. Kirsop!

Limping through the season is perfectly reasonable until it quits altogether. I hope you make it and then methodically go through the whole system this winter. Do not neglect the state of fuel and crud likely in your tank. When we first owned our boat, the PO told us he always added Biobor when he added fuel to the tank. We never had a clogged fuel issue but one winter, bored and with too much time on my hands, I decided to install a fuel tank inspection port. This was also done to remove the busted and clanking tank baffle I found by removing the fuel gauge sending unit. I was really surprised by all the gunk I found in the tank and so glad the filters appeared to be handling it.

Be methodical in your approach, but fix the obvious without question. Will you be able to run the boat in the water? ...hmm, Traverse City...prolly not this winter. Idling and running unloaded in the driveway on the trailer doesn't tell you very much other than you have successfully bled the system, which I would definitely do before splashing it.

Since cleaning the tank shiny spotless a couple seasons back, the filters still catch visible crud. I need to re-inspect the tank this winter just to see what's growing in there. I highly recommend adding an access panel.

[Plum76]

That’s the plan Willie, finish up the year (likely about a month of limited cruising) and take care of some fuel tank issues prior to winter. Planning on removing tank and cleaning, adding inspection port and resealing all the threaded boss connections on top, they all weep a bit when tank is full. Have some threads to clean up and retap on the gauge fixing mount too, that weeps a bit as well. Have already replaced the vent line, and likely to replace all the fuel lines as well.

Jason

$68 USD! Buy two and sell one to Mr. Kirsop!

Limping through the season is perfectly reasonable until it quits altogether. I hope you make it and then methodically go through the whole system this winter. Do not neglect the state of fuel and crud likely in your tank. When we first owned our boat, the PO told us he always added Biobor when he added fuel to the tank. We never had a clogged fuel issue but one winter, bored and with too much time on my hands, I decided to install a fuel tank inspection port. This was also done to remove the busted and clanking tank baffle I found by removing the fuel gauge sending unit. I was really surprised by all the gunk I found in the tank and so glad the filters appeared to be handling it.

Be methodical in your approach, but fix the obvious without question. Will you be able to run the boat in the water? ...hmm, Traverse City...prolly not this winter. Idling and running unloaded in the driveway on the trailer doesn't tell you very much other than you have successfully bled the system, which I would definitely do before splashing it.

Since cleaning the tank shiny spotless a couple seasons back, the filters still catch visible crud. I need to re-inspect the tank this winter just to see what's growing in there. I highly recommend adding an access panel.