Fuel pump or anti-siphon valve problem?

Took the boat out this afternoon with some of my coworkers. The boat started, but sputtered to a stop within a minute as I was loading people. Restarting worked, but would work for shorter and shorter periods of time. Eventually, it wouldn't restart. Sniffing the carb proved that there was no fuel.

I've had a problem like this before that was solved (maybe not?) by changing the anti-siphon valve. So, I jumpered the fuel pump relay and heard the pump run for a few moments and come to a slow stop. I tried to pull off the fuel filter but it wouldn't budge (by hand). I put this on myself a month ago, and know that it was not that tight and the gasket was oiled. The only thing that I can think of is that the fuel pump was pulling a vaccum on the intake side of the pump. Opening the fitting to the metal fuel line proved that there was no fuel in the system.

I opened up the access plate to the top of the tank and rapped on the check valve a bit (some frustration was evident). This seemed to fix the problem as I was able to jumper the pump and get fuel up to the output side of the pump. I put everything back together and the boat ran just fine.

Is this a normal failure of an anti-siphon valve? The previous one seemed to leak back to the tank if I didn't use the boat for a couple of weeks. The last time that we used the boat prior to this evening was 3 days ago and it ran just fine.

Your thoughts and ideas will be appreciated.

johnbo

Re: Fuel pump or anti-siphon valve problem?

Anti-Siphon valves get foulded by fuel tank junk.

I think you answered your own question. You had a serious vacuum on a fuel supply that couldn't deilver.

Re: Fuel pump or anti-siphon valve problem?

Over the past week or so (vacation time), I had the boat on the water 6 of the last 10 days. Ran and started prefectly. However, on Sunday, the same problem returned.

Basically, the engine will start easily, but while I'm loading the kids, the engine will die, subsequent restarts won't run for too long. I opened the steel line at the top of the (electric) fuel pump and it was dry as a bone. Jumpering the fuel pump with the output line open would run and run with no output. Hammering on the anti-siphon valve had no effect. I pulled anti-siphon valve off the tank and found it prefectly clean. Could easily blow in one end and that end would hold a reasonable (mouth applied) vaccum. Put everything back together and tried to prime and it worked. Boat ran great for the rest of the day, even after a couple of restarts after a couple hours of fishing.

I pulled the anti-siphon valve off tonight and also pulled the pick-up tube and it was prefect, not a speck of dirt.

I'm going to re-install my vaccum guage tomorrow, so that I can see what is going one when it fails next time.

At this point, I guess that I'm trying to prove that I've got a fuel pump problem. The tests/experience so far seem to point away from the pick-up and anti-siphon (which I replaced earlier this year when the problem first occurred). At the current price of about $180, I'd just like some confirmation that I'm heading towards the right solution.

Is this a typical failure mode for these Volvo Penta electric fuel pumps? I get good power out of the engine, so I don't believe that I have a delivery problem (once I get started).

Help?

Thanks,

johnbo

Re: Fuel pump or anti-siphon valve problem?

johnbo said:

I'm going to re-install my vaccum guage tomorrow, so that I can see what is going one when it fails next time.

Click to expand...

This is the correct way to test. You need the guage installed so you can see what is happening "when it fails". If it doesn't start and you have NO vacuum it's either the fuel pump not sucking or a leak in the fuel line (kind of like having a hole in a drinking straw). Over 4 inches of vacuum means there is a restriction between the gas in the tank and the fuel pump.

Re: Fuel pump or anti-siphon valve problem?

Thanks for the feedback. I'll install the vaccum guage this evening along with the transparent fuel line section. Just a little nervous about leaving this attached with the engine cover one, because the transparent fuel line is certainly not CG approved. I'll just try to zip tie the lines away from the moving bits.

Thanks,

johnbo

Re: Fuel pump or anti-siphon valve problem?

John, My fuel pickup tube has a SS strainer located inside of it, not at the far end as one might expect. I needed to unscrew the pickup tube from the elbow, to clean out the junk that clogged it.

Re: Fuel pump or anti-siphon valve problem?

Hi Chris,

Mine had a SS mesh 'hat' that wrapped around the bottom of the plastic/rubber pickup tube. There was about a 1/2" gap from the bottom of the mesh to the bottom of the pickup tube. It was as clean as I could possibly imagine it. Not even a spec of dirt or sediment. Not bad for a 10 yr old boat. It looked brand new (could be for all I know about the previous owner).

Thanks,

johnbo

Re: Fuel pump or anti-siphon valve problem?

The anti-siphon valve is a $15 part that is prone to failure. I would replace it if there were any question about it. I'm told the brass valve lasts longer than aluminum.

Re: Fuel pump or anti-siphon valve problem?

Hi Dave,

In a previous post, I had thought that I had found the source of this problem and had replaced the prior anti-siphon valve with a new one ($8 at the local hardware store).

I've got all of the pieces to set up a vaccum guage on the fuel line that I can operate the boat with. The only thing that I'm short of is time. I'll install this tomorrow evening, I hope, and see how the fuel pump is operating. when and if it fails to start.

Later,

johnbo

Re: Fuel pump or anti-siphon valve problem?

So, I installed my vaccum gauge and a short bit of transparent fuel line right underneath the fuel filter. I'm still in the garage, so I jumpered the fuel pump to see what would happen.

I watched the fuel level in the transparent hose come up to within about 3 inches of the level of the fuel filter and stopped rising. The vaccum guage read about 2 inches. The fuel pump contained to run.

I pulled the metal line off the fuel pump and the carb and verified that it was clear of blockages. I also pulled off the carb inlet filter and it was clean. I reassembled everything, but left the connection between the fuel pump outlet and the metal line open. Jammed a rag up against the pump outlet.

I jumpered the pump again, and it pulled the fuel right up through the pump and saturated the rag and more... I shut off the pump and cleaned up the mess.

I reconnected the metal line to the fuel pump and jumpered the pump, this time the fuel level (which must of dropped while I was cleaning up) came up to about the same 3 inches below the fuel filter and stopped moving.

At this point, the only thing that I can think of is that the pump is worn out or damaged, in that it can't pull hard enough against the fuel when there is the slightest bit of back pressure.

Does this make sense?

Is this the way that these pumps fail?

Thanks in advance.

johnbo

Re: Fuel pump or anti-siphon valve problem?

Disconnect the line from the carb again and push a tight fitting rubber hose onto the steel line, then hang the rubber hose into a bucket to catch the fuel (instead of the rag like you previously did), jumper the pump, when the fuel starts flowing, pinch off the supply line between the fuel tank and the pump. What does the guage read now ? The pump should be capable of pulling around 12 to 15 inches of vacuum (primed with fuel and pinched off).

If it does not, replace the pump. If it does, you will need the check the output pressure of the pump with a fuel pressure guage.

Re: Fuel pump or anti-siphon valve problem?

Great idea, don't know why that didn't cross my mind. Too much 'night boating' probably. I'll run the test tonight. My vaccum guage is also a fuel pressure guage as well, so I should be able to set up both tests, if needed.

Night boating is my wife's term for me sitting out in the boat in the barn at night fiddling/fixing/daydreaming.... Especially during last winter when it was below freezing.

Thanks,

johnbo

Re: Fuel pump or anti-siphon valve problem?

Ran the test that Reel Poor suggested. With the output of the fuel pump going into a gas can, the intake vaccum read about 4 inches. If I pinch off the supply line, the vaccum will rise to about 10 inches.

For the next test, I let the fuel level in the supply line drop into the transparent section of the supply line, took about 5 minutes. Then I pinched off the output line at about 1 foot from the pump (figured that this would be the same as the float valve closed in the carb). This time, the fuel level came up about 1 inch at 2 inches of vaccum, but would not rise high enough to prime the pump.

At this point, I'm stumped. The behaviour of the pump seems about right. Unless it is an intermittant failure. With the current operating mode it would seem that as the carb used the gas in the float bowl, the needle valve would open and the back pressure on the outlet would drop allowing the pump to prime. Except when it doesn't.

Even though the fuel system seems spotless, should I look at the needle valve in the carb? During the last failure, I rapped on the float bowl right in the area of the needle valve pretty good with the plastic end of a screwdriver, with no obvious change. This would indicate that either that this is not the source of the problem or that the needle valve is really hung up. However, if the needle valve was in this bad of shape, I would expect that the engine wouldn't be running very well and this it is really running well, once it gets started.

Any thoughts?

Thanks in advance,

johnbo

Re: Fuel pump or anti-siphon valve problem?

johnbo said:

Ran the test that Reel Poor suggested. With the output of the fuel pump going into a gas can, the intake vaccum read about 4 inches. If I pinch off the supply line, the vaccum will rise to about 10 inches.

Click to expand...

Did the pump have any problem picking up the fuel ? If no....
This test passes if you did not see any air bubbles.

johnbo said:

For the next test, I let the fuel level in the supply line drop into the transparent section of the supply line, took about 5 minutes. Then I pinched off the output line at about 1 foot from the pump (figured that this would be the same as the float valve closed in the carb). This time, the fuel level came up about 1 inch at 2 inches of vaccum, but would not rise high enough to prime the pump.

Click to expand...

This is an insignificant test. If the pump can't expell any fuel it surely can't draw any from the tank.

johnbo said:

At this point, I'm stumped.

Click to expand...

Move the guage to the pressure side of the fuel pump (still disconnected from the carb). Jumper the pump, with the fuel flowing plug/pinch off fuel flow at the outlet end of the pressure side hose, read the pressure guage, should read 4-7 lbs. If it does, shut down the pump (leaving the hose pinched closed) and note whether the fuel level in the suction side hose will drop. Make sure the outlet end that is still pinched/pluged does not leak, any.

Is this a 2 or 4 barrel Holly carb ?

Re: Fuel pump or anti-siphon valve problem?

Hi Reel Poor,

I wasn't 100% certain that I understood what you were asking for in:

Did the pump have any problem picking up the fuel ?

Click to expand...

When I started that test, the fuel level zipped right through the section of transparent fuel line and into the pump. I thought that I saw one tiny bubble, but it didn't repeat and was probably stuck to the side walls of the fittings as the level went up.

Moving on to the suggested test. I rigged up a port in my fuel pump outlet line (normally goes to the fuel can), so that I can attach my vaccum/pressure guage. Since the fuel level had receded back down the intake line from last night, I left the vaccum gauge in the intake line and started the fuel pump.

What I saw is an exact symptom of what I see when the boat won't run at the ramp. The pump ran and started to slow down after 10-15 seconds. At about 30 seconds, the pump came to a stop. At no point during this did any fuel appear in the transparent section of the intake line. The output line was still connected to the open gas can, so there was no head pressure. The vaccum gauge was reading almost nothing (maybe less than 1 inch). I placed an ammeter in the fuel pump line and saw a starting current of about 1-2A and would peak at about 8A when the pump stalled. The wiring harness has a 6A breaker, but this is bypassed by my test switch as my power comes from the back of the alternator.

I then took my MightVac and hooked it to the fuel line that was going into the gas can and pulled a 2 inch vaccum. Didn't see anything, and raised the vaccum to about 4 inches. This took a bit of pumping (5-6 strokes), but within a few seconds the fuel appeared in the transparent section of the intake hose. I think that I removed the vaccum before the fuel got to the pump, but I'm not sure that I did this in time.

Somewhere in this process, I tapped the upper end of the fuel pump with a plastic end of a screwdriver, thinking that this might unstick a valve or something.

Turning on the fuel pump caused it to pump fuel to the gas can.

I then setup the last test that Reel Poor suggested. I moved the pressure guage to the output port and capped its port on the intake line. With the pumped primed and pumping fuel into the gas can, I pinched off the output line. I about 4 psi of fuel pressure. The ammeter read about 2.1A at this point. The fuel pump continued to run.

I verified that no fuel was getting past the pinch point (2 smooth finished wrenches on either side of the line with a set of vice grips squeezing the wrenches together). I turned off the fuel pump. After letting it sit for about an hour, the fuel level has dropped down to the top of the section of transparent hose. (there are so many fittings in this setup, it is entirely possible that one of them is not completely sealed).

I wish that I knew what was inside of one of these pumps, then I might be able to match a failure to a part. Not to fix it, but to explain it.

At this point, the fact that the pump would not pump and stalled with an open output line, makes me think that there is a valve, like a check valve, that is getting stuck and causing the pump to build pressure against it. Since its not pumping, its not going to move any gas. I don't know if it was the rap on the upper end of the pump or the application of vaccum to the output side of the pump that unstuck it. I kind of wish that I had tried the pump between these two things.

This does seem to point pretty hard at the fuel pump. Do you agree?

Oh, your last question, this is a 2 barrel Holley carb.

Thanks,

johnbo

Re: Fuel pump or anti-siphon valve problem?

johnbo said:

I rigged up a port in my fuel pump outlet line (normally goes to the fuel can), so that I can attach my vaccum/pressure guage. Since the fuel level had receded back down the intake line from last night, I left the vaccum gauge in the intake line and started the fuel pump.

What I saw is an exact symptom of what I see when the boat won't run at the ramp. The pump ran and started to slow down after 10-15 seconds. At about 30 seconds, the pump came to a stop. At no point during this did any fuel appear in the transparent section of the intake line. The output line was still connected to the open gas can, so there was no head pressure. The vaccum gauge was reading almost nothing (maybe less than 1 inch). I placed an ammeter in the fuel pump line and saw a starting current of about 1-2A and would peak at about 8A when the pump stalled. The wiring harness has a 6A breaker, but this is bypassed by my test switch as my power comes from the back of the alternator.

Click to expand...

If i'm reading your statement correctly, this alone points to a faulty fuel pump.

Re: Fuel pump or anti-siphon valve problem?

Hi Reel Poor,

Thanks for the confirmation, this is pretty much the same conclusion (with a lot less experience) that I'm coming too. I'm going to order a new fuel pump tonight and see if that will fix the problem. I'll post back when I get it in.

Interesting observation - My local marine store had three fuel pumps in stock (at $210 each). Said that they sold less than one per year. Found that they didn't stock the O-rings that are used to replace the pump. Seemed like an odd choice of stocking. I would have assumed the other path. Probably going to go mail order, I like these folks and they are handy, but at $60 higher than mail order, its a little tough to justify.

Reel Poor, thanks for your advice on this. I owe you a beer or three...

Later,

johnbo

Re: Fuel pump or anti-siphon valve problem?

Naw, you don't owe me anything. Just post back and let us know what happened.

Well on second thought (about the owe) just help someone else if your there when they need it.

Re: Fuel pump or anti-siphon valve problem?

Quick note - The mail order fuel pump arrived from FL (FuelPumpKing) in 3 days, but one of the required O-rings is on backorder from the local marine shop. I'm not going to open the system until I get all the parts.

More later,

johnbo

Re: Fuel pump or anti-siphon valve problem?

:'(