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halyardz · 26-09-2005, 02:56

I'm about to emark on a project to spiff up the fuel system, including new lines, perhaps a larger vent, fuel pump etc. I have a few questions and would appreciate input. The engine is a 1980 model Universal 5424.

1. Fuel vent & line. I get overflow on deck while filling. Should I go one size larger with both hose and vent?
2. Got a recommendation to replace old electric fuel pump with a new, higher capacity one from NAPA. Sound right?
3.Is there a specific marine grade fuel line hose or is conventional (for diesel trucks) hose ok?
4.Fuel tank. Have been advised to remove the standpipe from the tank and remove the screen (if present). One opinion suggests adding a plastic hose at bottom so it will lay on bottom of tank. Sound OK?

Many thanks in advance. JR

Talbot · 26-09-2005, 03:23

I constructed my fuel tank so that the point of suction was 1/2" from the bottom of the V section at the base of the tank. This gives it a chance not to pick up any grot (unlikely as I filter all the fuel I put into the tank) I reckon that I lose abt a pint of fuel from the botttom because of this!

**GordMay** · 26-09-2005, 05:13

Paraphrased from ABYC Section “H-33" ~ Diesel Fuel Systems:

- Flexible Diesel Fuel Hose shall comply with the requirements of UL 1114, Marine Flexible Fuel Line Hose (USCG Type A), or SAE J1527 [size=1]Marine Fuel Hose[/size, and be so marked.
Metal,fuel lines must be Aluminum or Copper (min. Schedule 40), or Copper Alloy (min. wall thickness 0.032 inch or 0.81 mm)

- Minimum inside diameter of Vent Lines shall be 7/16 inch (11 mm).

**Pblais** · 26-09-2005, 16:22

You get overflow from too much fuel filling too fast. I always have an absorbant pad on the vent when I fill. If you put too much in it overflows, it's not a design problem it's an operator problem. My vent whistles as you fill and when it stops you need to stop filling. It's a PITA to be that quick so I deal with the overflow from the vent. It's going to happen so be ready and don't spill fuel in the water.

Strygaldwir · 26-09-2005, 17:55

I think dependability is the watchword on replacing the fuel pump. The only thing a higher fuel flow volume will do for you is send more excess fuel back to the fuel pump. There are some benefits to this, maybe? You filter the fuel more often, and you ostensibily might have lower fuel temperatures. This lower temperature "might" result in some extra power. (Although I VERY much doubt this in the Aspirated diesel engine). I would not replace it unless the flow was bad to begin with, or, you suspect the pump is about to go and want to do it for preventive reasons.

As Gord and Pblais pointed out a BIG no on going to the bottom of the tank. Even though we screen, filter, polish and pray our fuel is clean, some degree of sediment seems to always form in it. If not sediment, it is mosture coming out of condensation and falling to the bottom. If you put the pickup on the very bottom, you'll be trying to filter this stuff out in your filters and such. It is much better to try to leave it on the bottom and hope the sloshing doesn't cause it to be picked up and clog your filters.

Keith

26-09-2005, 20:43

It sounds to me like among other things, you are lookiing for more power out of your engine. A higher volume feed pump will only help if you do not have sufficient flow with the current pump. Check with the manufacturer. Too much volume can cause other problems. Damage to seals in the injection pump for one. If you want to improve the efficiency of the feed pump, make sure it is mounted as low and close to the tank as possible. These pumps blow far better than they suck. As for changing the pick up, screens are fine. If you are plugging a screen, it is time to clean the tank. If you switch to a straight hose, when the crud does get sloshed around, and it will, it will feed directly into the filters. As for the vent, again, the engine can only draw so much fuel. no sense putting a bigger hole in things that do not need it. He bigger the vent, the more moisture can be sucked in. You only need enough venting to displace the fule used with air. If you were running twin 500hp Cats, I would really consider these things, but for the little diesel you are running, these mods would not pay off.

halyardz · 27-09-2005, 00:40

Yes, the power is a bit on the low side and I'm about 250 rpms (includes 50+ fudge for age of engine) lower at max throttle than specs indicate. We've checked the prop, even pitched down. No improvement. Hull speed should be just over 7kts we are lucky to get a consistent 5kt.

Odd thing (at least to me)...is that when first running in gear, the rpms jump a bit. After running for 10 minutes rpms (top) drop about 50-100.

Filters were changed.

Vent: I hear you on the vent. No whistle on mine, it just surprises you with overflow...by the time you hear the gurgle, its too late and we do use pads when fueling. Thought a bigger vent line would help a little but understand the issue of letter more moisture in. We do have a Racor.

I feel a little "dumb" when it comes to such engine problems but am willing to tear into things and learn. (Except will not fiddle with injectors). Jim

**Alan Wheeler** · 27-09-2005, 01:38

Hi Jim, there are many reasons why you may have the low RPM problem. Unless you have exhausted all the other possabilities, I would place the Diesel fuel supply as the lowest on the list. Assuming ( as you said) the filter has been changed. I take it that your engine once did run at "normal" RPM and this is now lower than the old "normal". How does the engine rev at full throttle but in nuetral. Will it run to max RPM or still slower than it should? A ruff rule of thumb,and this is assuming the propellor is spec'd correctly, the difference between a max no load and a max loaded engine RPM should be ruffly 200RPM. Now I do emphasise the "ruff rule" part, cause there are many variables.
Soooo... things to check. Firstly, is the engine exhaust abnormaly smokey and what colour is the smoke if yes?
Air intake supply is a biggy, deisels need lots of air. Check the aircleaner and vents to the engine room.
Howbout the injectors and injector pump. Now something that can happen with age, there are often springs inside the injector pumps that can change tension due to heat and age. This can change the fuel dosage to the engine and thus change power.
And finally, compression. Maybe the engine is just getting really tired.
Of course, most all of these possable faults will, or should be acompanied by the tell tale smoke fromt eh exhaust.

Deisel vents. Well you have had good advice. The big issue with Deisel when being poured, is that it foams something chronic. The foam fills the tank and gets forced up the spout. There is a cool little trick that can be made to fit to a tank, but I am unsure if it can be used in a Marine application. So becareful. Have the breather pipe connect from tank to a small container that acts like a buffer. At the base of this small container, a bleed hose goes back tot he tank to drain deisel from it back to the tank. On the otherside of the container, the breather hose continues on to the breather cap or what ever you have on the end of the hose. What happens is that the foam traveling up the hose has well and truely turned back to liquid and falls to the bottom of the small catching container and drains back to tank.

27-09-2005, 18:18

Wheels brought something to mind, now that I know what issue you are addressing. A coule of years ago, my engine started loosing power, and heating up. I checked al the usual stuff, but found no problem, then I happened to look in the aft lazerette. I keep my bigger ground tackle in there, and the 65# fisherman had moved, and was on top of the exhaust hose. the hose was severely restricted, but was letting enough water through to lead me to believe that the cooling was working OK.
Check your exhaust hose for kinks, also, if the engine has never reached the RPM it should, check with a dealer to see if you have a large enough diameter exhaust for the engine. This is one of those elusive problems often built into a boat, or as a result of a repower.

halyardz · 28-09-2005, 21:17

Kai & Alan: No smoke. Exhaust looks fine...no white, no black. I changed the lift pot muffler and checked the exhaust lines. No problems. Even pulled the exhaust manifold (or whatever that thing is called) off and checked for carbon deposits last year. OK there. Starts like a champ. Air intake is not a problem with this unit. There is no air filter. Looks like it came from the factory (in 1980) without one. There is a little debris screen but that's only to keep things like chunks of broken belt out.

This is great information you guys are providing and I sincerely appreciate your time and effort. I guess the next stage is to get a mechanic in there and see if its injector related. I'm almost certain they haven't been replaced over the life of the engine.
Jim

**Alan Wheeler** · 28-09-2005, 22:40

If it's done high hrs and injector systems hasn't ever been looked at, then it could well be the area of concern. If you have reasonable mechanical ability, you could remove the items yourself. Injectors are easy to take out and put back in. The injector pump is a little more tricky due to timeing. But if you mark the shaft and ensure the same marks are lined up when refitting, it's hard to go wrong. However, a mechanic can check everything over if you get one to do the entire job. The cost should not be horrific. It's best to do both Pump and injectors as the pump can be checked for calibration.

Will Burton · 30-09-2005, 11:54

You might want to check out the Racor LG100 fuel/air separator to solve your overflow problem. Even when fueling slowly, I had a problem with fuel overflow that was solved by the Racor unit. It's like a check valve that you put in the fuel vent line. When fuel comes up the vent line, it shuts it off and trips the fuel fill nozzle. Solved the problem for me. Available at www.go2marine.com.

30-09-2005, 19:24

Good luck Jim. A check of injector pump pressure, and of your injectors may solve the problem. Wheels is right about the injectors, but you may as well have it all checked at once.