Bad Fuel Pump? Volvo Penta 7.4 Gi

[Flydino]

Hi, first time poster here! But i have learned many things from this forum.

Here is the problem, I have a 1999 Larson Cabrio 270 with a Volvo Penta 7.4Gi engine.

I was out last Sunday when my engine started sputtering(it sounded like it was running out of gas) and then died and would not restart. It has plenty of gas in the tank. It will crank but no combustion.

Unfortunately I had to get towed back in.

With the advice I got from this forum I purchased an in-line spark and ignition tester. I hooked it up to a spark plug on the engine and tried cranking the engine. It flashes when cranking so i have a spark right? My ingnition coil should be ok?

So it must be a fuel problem right? Since the eninge wont start i cant do the pressure test. I checked the fuel line from the fuel tank to the fuel filter and it is clear of obstructions. When i turn the key the high presure fuel pump at the back of the engine turns on for 2 senconds.

So i am guessing the problem is the low presure fuel pump. Does this sound logical? is there a way to test a fuel pump to see if it is defective? Since the HP fuel pump is making noise when i turn the key it probably is not the problem?

 

[Haut Medoc]

Re: Bad Fuel Pump?

Re: Bad Fuel Pump?

Welcome to iboats......
Try posting 'Volvo" in your header to catch Don S attention, he will have an answer for Volvo stuff.....​

 

[Bondo]

Re: Bad Fuel Pump?

Re: Bad Fuel Pump?

Ayuh,........

And change the Fuel Filters 1st,..........

 

[Don S]

Re: Bad Fuel Pump?

Re: Bad Fuel Pump?

You have 2 pumps on that engine a high pressure pump on the rear of the engine and a low pressure pump on the front. You will need a special fuel pressure gauge to test the pressures, but, is the front pump running for 2 seconds when the ign. switch is turned on?

 

[Flydino]

Re: Bad Fuel Pump? Volvo Penta 7.4gi

Re: Bad Fuel Pump? Volvo Penta 7.4gi

Thanks for the replies.

The fuel filter was replaced 3 months ago but that is something i will try replacing.

Don, the High presure fuel pump at the back of the engine makes noise when i turn the ignition on but the low presure pump, the one at the front of the engine where the fuel filter is, does not make any noise when i turn the ignition on.

 

[Don S]

Re: Bad Fuel Pump? Volvo Penta 7.4gi

Re: Bad Fuel Pump? Volvo Penta 7.4gi

Do you have power and a good ground to the front pump for those 2 seconds?

 

[Flydino]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

Hmmmm....I will check the ground wire tomorrow. Is there an easy way to check for power? Can I use a simple power tester like i would use in my home to see if an outlet is hot or not?

 

[Reel Poor]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

Most likely, if the high pressure pump is running the low pressure pump has power to it, unless there is a wire or connector problem. They are both powered from the same relay. Disconnect the wiring harness connector from the low pressure pump and with a volt meter or a test light check for voltage. Connect the meter/test light ground wire to the black wire (ground) and the meter/test light positive cable to the yellow with green tracer (12 volt power source). Turn the key on and read the meter within the two seconds the the high pressure pump is running. You should also have power here while cranking.

 

[Flydino]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

Well it looks like i need a more sensitve volt meter, but before i go out and spen 40 bucks on a volt meter let me run this by you.

To test the Low Pressure fuel pump can I remove it and attach it to the High Pressure fuel pump electric. Then turn the ignition on and see if it makes any noise? If it makes noise then its a wiring problem. If it doesn't make any noise then I know I have to replace the Low Pressure fuel pump.

Sound reasonable?

 

[Reel Poor]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

It sounds reasonable, but I have never tried it. I don't know if the connectors are the same or not, although I would suspect they are. One thing I can tell you is, these pumps can be damaged if they are run dry (without fuel flowing through them).

 

[Don S]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

The connecter is the same on the high and low pressure pump. but the wires sure aren't long enough to reach the other pump. And trust me, pulling that high pressure pump off the VST isn't that easy a job.
All you need is a test light to check the power to the low pressure pump. Just disconnect the high pressure pump so it doesn't even try to run. Then hook a test light to the connecter for the low pressure pump and see if it lights up for a couple of seconds when you turn the key on.

 

[Flydino]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

Yep, bad fuel pump. The electric is ok. And to double check, after i removed the Low Pressure fuel pump I pluged it into the High Pressure fuel pump electric and turned on the ignition. It made no noise.

 

[Reel Poor]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

Something else to think about. I always prefill my fuel filters to keep the pump from running dry. The time it takes to prime a new fuel filter is enough to cause damage to a pump. And they don't like water either.

 

[Flydino]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

Thanks for the tip! I'll remember to do that and pre-fill my fuel filter.

 

[Harleyridertex]

Re: Bad Fuel Pump? Volvo Penta 7.4 Gi

I will say I am really dissapointed in volvos design for a marine fuel pump system..... It is not like you can just get out and walk when one of those whiney suckers decides to retire...... I was warned by a whine that was not normal...... For about 2 minutes...... then I was swimming......
Now to be honest i caused all my problem.... I had a low pressure pump fail 5 years ago...... Now I remember dumping the fuel filer looking for trash and water...... Not in the lake either......
Other day i pulled filter off to see if any water in it as my pump was sounding funny......Whiney above engine noise..... I actually was worried the outdrive was low on oil or something...... I didnt prime fuel filter when I put it back on..... I checked temperature on pump and it was really hot.....Fuel lines going to high pressure pump was hot too....... Told me vapor lock of sorts........
I checked all the flack on here...... One thing I will say is.....PRIME YOUR FILTERS BEFORE INSTALLATION....... BLEED FUEL SYSTEM......I know mine was whining before and I understand the design of a high speed pump that without any load of pumping fuel will become a ..... RUNAWAY HYPERSPEED PUMP TILL IT TRASHES....... My Fault completly......
When you get thru kickin yourself and cussin....... Measure or remove just the punp off the stand....... It will come off even if you have to bend top of bracket a bit........ Go to Auto place and ask for a inline pump that has a pressure of 5 to 6 pounds..... feeds 30 gallons a hour or more...... I had one in the Garage that I almost threw away a dozen times....... Normally about 30 dollars........ It is not a high speed pump....... It clacks side toside when empty but is silent when it runs........ My problem is solved
I will say that i noticed a strange Idle and a surge the last few times i was out...... I just figured it was the wonderful fuel we are forced to burn now......With the whine and the no idle...... Restart alot..... I thionk it was the fuel pump that was reaching maturity........
Volvo over enginerred this engine...... It is up to us to rigger rig it to suit our needs....... Go get a cheap pump.......650.00 is rediculous......They both could leave you swimming
If any one has a question let me know......... Is Volvo still owned by Krauts