Volvo 7.4 gi sometimes great other times not

[LEAKITIKI]

This boat is still new to me and Im chasing an intermittent problem. On a recent lake outing it went like this. Day one, took boat out for first time. Baot had to be repaired prior to purchase as there was a crack in the keel. Tank was drained and removed during repair. So she had a full tank with fuel additives. It ran 45 mph at about 4300 rpms. Seemed like she had more.
Day two, Started out great. After a short time on the water I was getting 50 mph at about 4600 rpms. Sat in the shade for a while and went for another drive about. Only 40 mph. Check and cleaned spark arrestor as entire engine hold was coated in sanded fiber glass. Still no luck.
Day three. New plugs. Boat started where I left off and then came to the party. Spent the last two hours running 55 mph with no issues.
Currently, having problems with acceleration with muffs on trailer. I have been working with a mechanic friend to resolve. I have checked post and talked to varrious people. Most indications are problems with the fuel pump(s). I tested pressure on the pumps and it falls out of spec. when you attempt to accelerate. The manual states that boat must be on water, under load to test. Why is this?

 

[tkrfxr]

Re: Volvo 7.4 gi sometimes great other times not

On the trailer, don't accelerate too much......there may no be enough water to keep up with your RPMs....

I would look to resolve "acceleration problems" with the boat in the water....

 

[LEAKITIKI]

Re: Volvo 7.4 gi sometimes great other times not

Water temp has not been an issue. As you increase gas the pressure drops too low. My mechanic says that problem will only get worse on the water. However the manuals says to test the fuel pressure it must be on water. Whos right?

 

[tkrfxr]

Re: Volvo 7.4 gi sometimes great other times not

The manual is right...your mechanic is lazy...

 

[bransjeep]

Re: Volvo 7.4 gi sometimes great other times not

Sounds like restricted fuel flow. Maybe your fuel filter/ or fuel pump is getting lazy

 

[Don S]

Re: Volvo 7.4 gi sometimes great other times not

There are several versions of the 7.4Gi, if you post the full model number or the Volvo serial number we could get you the correct information.

 

[LEAKITIKI]

Re: Volvo 7.4 gi sometimes great other times not

YO Don GLad to see you here I need your input prior to throwing parts at the boat.
Prod # 3869060
Type 74GI PEFS
Ser # 4012007292
Thank you

 

[Don S]

Re: Volvo 7.4 gi sometimes great other times not

IF you don't have good fuel supply to the pumps, you sure aren't going to get good pressure from the pumps. If pressure is ok at idle, I would be looking at the fuel supply side, either air leaks (loose hose clamps?), plugged pickup tube, dirt picked up from the fuel tank when it as removed and put back in, and is now on the pickup tube.
To check, run these tests (ON the Water), testing without a load on the engine isn't testing, it's just running the engine and killing time.
http://forums.iboats.com/showthread.php?t=283269

PS: You can download the OEM service manuals for your EF model, up in the Adults Only sticky. In the Volvo info section.

 

[LEAKITIKI]

Re: Volvo 7.4 gi sometimes great other times not

I need some help understanding this. While trying to get the boat to run right over the weekend I found a wire that was corroded and came off the ignition accessory side of my switch. While inspecting the wires the starter lead broke off. i ran the wires thru my meter and showed 10.6 volts not the 12.2 I saw at the hot lead. I went to an auto store and bought a new ignition. The switch however would not engage the starter, its rating was 15 Amps. On monday when the boat store was open I bought a 30 Amp. switch. Put it on last night a put the boat on muffs. It now starts right off the bat. Fuel pressure high side is 40 and hardly drops when accelerating. Boat runs right up on Rpms with no hesitation or flat spots. Could it be that simple???

 

[bransjeep]

Re: Volvo 7.4 gi sometimes great other times not

Could be.. What color was the wire that corroded off?

 

[LEAKITIKI]

Re: Volvo 7.4 gi sometimes great other times not

first wire was red...but it butt slices to a orange that travels to the rear of the boat. That wire was off during several runs on the water. It was hooked to the accessory side or constant hot of the ignition. The next wire was yellow( starter) so then nothing without a jumper.

 

[Don S]

Re: Volvo 7.4 gi sometimes great other times not

Orange is USUALLY an accessory wire that goes from the battery to the accessory fuse panel, and shouldn't really be hooked to the ignition switch at all. Almost impossible to tell how yours is wired.

What you should have to the ignition switch is a Red (or red/purple) wire from the engine to the battery terminal on the ign. switch, the yellow/red is start, and a purple wire should be there to power the ignition and the instruments.
There is a link up in the Adults only sticky for manuals for your engine here it is http://www.4shared.com/dir/14518190/c08a758e/EFsharing.html, look at the wiring diagrams.

Low voltage shouldn't have anything to do with fuel pressure, as the pumps do not get power from the ignition switch, but with low voltage going to everything else, you were probably lucky it ran at all.

 

[LEAKITIKI]

Re: Volvo 7.4 gi sometimes great other times not

If I did not give the Brain box constant/consiteint power would it cause strange operating conditions? Also I did use a new fuel pressure gauge on this last start up...not sure that had anything to do with it. The fuel pump is not as load now ... bit still has that GM high pitch but so did my truck for 80,000 miles... I would still like to check the dip tube and possible??ball. I just dont know how. Can I just pull the fuel pick assy. out and inspect? Is there anything special about doing that? Thanks to All...

 

[bransjeep]

Re: Volvo 7.4 gi sometimes great other times not

I dont know if your fuel pressure gauge is in line. But ive seen clogged ones. So that could have been restricting it as well

 

[Don S]

Re: Volvo 7.4 gi sometimes great other times not

I would still like to check the dip tube and possible??ball. I just dont know how. Can I just pull the fuel pick assy. out and inspect? Is there anything special about doing that?

Post a picture of where your fuel line hooks up to the fitting on the tank.