Fuel pump question

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WALSHIE

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I have twin 2001 Crusaders 5.7L 'captains choice' motors. The port side decided it does not want to run! I verified spark and it does run with ether. Fuses and relays are good. There are two fuel pumps, a low pressure and high pressure. Both pumps show voltage for a few seconds when the key is turned then shut down. This is apparenltly as designed since the starboard engine does the same thing! It's not the fuel filter (we switched them).

So,,,,how does this two fuel pump system work? Is there a sensor that engages the fuel as per pressure? If so, this could be bad. Why does the electric go on then off?

Another thought is perhaps a low oil sensor is faulty and the computer is shutting down the engine?

Any thoughts are appreciated.
 
I was sure my fuel pump was cycling off before I had fuel pressure. I was wrong. I thought I had good spark, because with a timing light on the plug wire, the timing light was firing. But it would not start. My first guess was not enough fuel pressure from the pumps. I determined I was wrong by renting/borrowing a fuel pressure gauge from autozone - it attaches to a valve on the fuel rail, forget what it’s called, but it looks like a tire valve.

Then I thought perhaps my fuel injectors weren’t firing, so back to the autozone to borrow a set of noid lights, to test the injectors. They were firing. My parts guy let me borrow a coil, even though I swore I had good spark. He was right, while I had a spark, it was not a good enough spark to fire a cylinder full of gas. Motor has been fine since.

Love the autozone tool rental - essentially it’s free rental - you buy the tool, if you bring it back, whenever, full refund.

I assume this is a carbed motor? You need to get a fuel pressure gauge in front of the carb, and keep a timing light on the coil wire. Dump some gas in the carb, it should run for a couple of seconds, when it dies, was it because fuel pressure dropped, or spark stopped?
 
Thanks alk, I figured it out. Since I am hoping to go away this weekend, I had called a mechanic with the right tools to test the fuel pressure, injectors and perhaps read the on board computer codes.
This is fuel injected and some research shows me the two pumps work like this:
- Low pressure high volume fuel pump just fills the fuel cell canister
- The high pressure fuel pump fills the rails of the injectors
- At the end of the fuel rails is a pressure regulator that allows too high of a pressure to return to the fuel cells
- The fuel cell has a return line to the tank if it fills up

So, both fuel pumps should be running when starting and running all the time. There is nothing to turn them on/off and the pressure regulator is mechanical not electrical.

This afternoon, I took the fuel cell off, filled it manually and secured it. The engine ran! For about 5 minutes. Hmm, it did the same yesterday when topped off.
Sure enough the fuel cell ran dry....

I removed the hose from the output of the low pressure pump into the fuel cell, put it in a jar and had my daugter try and start it...no fuel! (BTW I verified filters were good yesterday)
So, with her at the key in the on position, I took a wrench and HIT the low pressure pump.....it worked!
I put everything back together and engine now works!! I am waiting for a new pump to be delivered.
Another tidbit, since both pumps cycle when key is on, it helps to disconnect power to each pump to hear them one at a time!!

Phew - called off the mechanic and ordered with express delivery!! Now I am very fluent in how this fuel system works.

Thanks again alk for the response.

Chris.
 
Ah, the old hit it with a big fn tool fix. Nice work!
 
Good work, Walshie!
Did you check the male & female electrical connectors on the LP lift pump for any corrosion of bent pins that might only provide weak current to the pump so any debris might stop it?

My 2 blue 5.7L MPI's (2003) have the returnless system option so they are set up a little differently than yours, but at separate times I replaced 1 LP pump and have had 2 HP pumps replaced- 1 on each engine. I took apart the LP pump and found it is a gear-type pump , not the same pump as yours but similar shape & size .
So I'm just wondering if you might just be able to open up your pump and see if there is any debris that might somehow have gotten past all the filters and prefilters to catch in the gears before you hit the case .

Probably friction in the motor part, but might be worth checking the pump part , at least so you could maybe keep it as a spare.
 
Good shopping, Walshie.

As I recall, I did the same thing and likely bought the reasonably priced identical version of the LP lift pump. Both have the connection terminals on the bottom ( where they can corrode unseen if the RW pump leaks) so I just disconnected and reconnected there , using the original pigtail with the plastic plug connector. Apparently that is a $300+ pigtail! :D

With no surprise , I believe there are much less expensive sources for the Pierburg HP pumps as well .
 
The price for marine parts is just outrageous! I priced just a Groco 1 1/4in bronze close nipple and my West marine 1996 catalog had it for $25. Their current internet price is $40. That's a 60% increase in just 4 years! I found it from a different source for $19. The marine industry is just killing itself.
 
That's why I like simple carbed engines with mechanical fuel pumps. The last one I replaced lasted 30 years, a Carter marine mechanical pump can be bought for about 100 bucks. That and a good clean properly adjusted Quadrajet.
 
Have to say, in general I greatly prefer the MPI engines which provide quicker more reliable starts, better economy and 60 more HP/engine over the same size Crusader 5.7L carbed engines I had. ( But part of that is the switch to Vortec. ) No more leak-down Q-jets and frequent choke replacements. As Walshie pointed out , the carter LP lift pumps for these engines can be bought new for ~$60, but the Pierburg HP pump replacements are higher.
My replacement MPI engines are 17 yrs old now and have well over 2800 hrs on them so I don't think they owe me much. The running carbed engines they replaced had 2750 hrs on them and were sold after removal.
We all have our preferences, doesn't mean either is wrong.

Are any new cars or trucks sold in the US still made with carbed engines? I bet that nice Jeep GC 5.7L Hemi doesn't have one. My Jeep GC 3.6L certainly doesn't. :D
 
We also have 1996 twin crusaders on our motoryacht. Tried to prestart before splashing 5 weeks ago. Port started 123 starboard cranked but wouldn't kick over. Mechanic checked it out and said we need new fuel pump. Quoted price of $1500. OMG ! 4weeks into repair we were told we need new manifold as he had trouble removing bolts from original. 5 weeks later are now being told we need new water pump! New price is at least double! Is this real? So discouraged now and wondering if we'll ever see the water.
 
I agree with what Sandy said. Sure the MPI has two fuel pumps but now that I understand how they work in tandem, I can debug much faster for next time. Bottom line, a carter pump is used to deliver the fuel to a canister which has a high pressure pump to the rails and returns to the canister. Quite simple actually. Plus there is a port for pressure gauge on the fuel rail to help further debug.

Harmsway - sorry to hear about the repairs. This is THE MAIN REASON I prefer to do my own. I troubleshoot down to the part and get it right 90% of the time. It's easy to guess when you are spending other people's money. Recently I helped another boater diagnose his fresh water (galley) pump but I was nervous, what if I was wrong? Like most things, I bench tested it to verify it was shot and found water inside the windings of the motor.

Good luck with your fix, it might be time to think of a new engine...or new mechanic.
 
After 6 weeks of frustration and a new water pump and manifold in addition to the fuel pump we are now in the water and home. She runs great and needs a major cleaning in and out. I could never figure out how the dirt gremlins get in through the shrinkwrap.
Only problem now is water in the bilge. There is no water
in the water tank, holding tanks are empty. So now what?
The water appears to be nasty from the canal. Any suggestions would be greatly appreciated.
 
quote:
Originally posted by harmsway

After 6 weeks of frustration and a new water pump and manifold in addition to the fuel pump we are now in the water and home. She runs great and needs a major cleaning in and out. I could never figure out how the dirt gremlins get in through the shrinkwrap.
Only problem now is water in the bilge. There is no water
in the water tank, holding tanks are empty. So now what?
The water appears to be nasty from the canal. Any suggestions would be greatly appreciated.

Click to expand...


There will most always be some retained bilgewater as the auto switch is mounted just high enough it will shut the pump off before the pump is completely out of water, otherwise it could run until the battery was dead. Plus of course there is always some drain-back from the discharge hoses and in many cases that quantity can be considerable.

Other common sources can be leaky bilge drain fittings,
prop shaft stuffing box /dripless seals,
Rudder shaft packing glands,
any thru-hulls, especially awful white nylon outlet or drain fittings near the waterline that crack & break off over time,
un-winterized split RW or FW hoses or their loose/broken hose clamps leading to low T/H fittings ,
Leaking T/H transducers,
leaking sea strainer lid o-rings,
leaking oil/ATF/fuel pump coolers or H. Exch. fittings, or RW pump,
no-longer-sealed deck to hull joint .

Not to mention hose-rinsing or rain water or sea spray draining down through leaky hatches, anchor lockers, sole storage compartments/ fish boxes, and livewells.

I'm sure there a plenty more potential sources but that's a start.
 
Many thanks for your suggestions. I will run them past the captain and hope something makes sense.
 
If you pump it out and the water comes back, that could be a problem. If not, perhaps the water is residual from all of the work you just had done...pulling off hoses to replace the raw water pump could be one culprit.

Clean the bilge and take another look. Glad you made it in the water! Happy Boating.
 
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