Fuel Pump not energizing

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sdhow · #1 Post by **sdhow** » Tue Apr 17, 2012 5:20 am

Thought I'd start a new thread, as cannondale32's topic started going all over the place.

Saw the posting in his topic where it was stated the fuel pump doesn't come on until the starter button is pushed. I swear mine pressurized the fuel rail when the ignition was turned to on and the run switch to the 'run' position. My bike ran, but intermittently wouldn't restart. I'd let it sit a day, then it would restart. Last time it ran, I ran it up and down the block and it cut out on the return run, like someone flipped the run switch to "off".

I suspected the pencil coil was bad and replaced it, but now I'm not getting the fuel pump to come on. Bench tested the pump; it works fine. If I'm to understand the wiring diagram, the + terminal on the pump is always hot; the - terminal is to remain ungrounded until the ECU opens the circuit, then it's grounded and turns on. I'm getting no ground at the B terminal at the CN16 connector.

ATV will start to fire with a squirt of starting fluid, but will cut out...just as if it's getting no fuel. Is there an issue with the grounding of the ECU, requiring a separate, more robust ground strap?

Let me recap what I've already done:

New injectors/seals
New vacuum lines
New spark plug
New pencil coil
New fuel lines (and seals on the quick connects)
New fuel filter
New air filter
New ECU relay
New fuel pump
Tested the ignition switch and took the run switch apart (cleaned and tested)
Replaced ECU with back up unit...no difference

Any thoughts?

speedracer · #2 Post by **speedracer** » Tue Apr 17, 2012 10:41 pm

If your fuelpump is priming with just turning the key on,something is wrong.Every Dale I had you needed to push the start button to get the pump to prime.From what you discribed,sounds like a wiring issue.I wounder if you can run a ground wire off the negitive terminal on the pump to a grounding point on the frame somewhere?On the quick connects,did you replace the o-rings as they can swell and restrict fuel flow.

who_gives_a6 · #3 Post by **who_gives_a6** » Tue Apr 17, 2012 11:32 pm

QUOTE (speedracer @ Apr 17 2012, 10:41 PM) <{POST_SNAPBACK}>

If your fuel pump is priming with just turning the key on,something is wrong.

The two quads I have running right now prime the pump when turning the key. Another I haven't got built yet, but did as well before teardown. Only my bikes have to hit the starter, due to no keys.

MX Quad Dad · #4 Post by **MX Quad Dad** » Tue Apr 17, 2012 11:55 pm

My quads don't prime until te green button is pushed.

I believe the ECU ground is at the left headlight, one of the lower bolts on the bracket that holds the light. I would check all the grounds. star washers are recomended. also try pulling the relay under the air filter.

Canniboomer · #5 Post by **Canniboomer** » Wed Apr 18, 2012 1:35 am

QUOTE (speedracer @ Apr 17 2012, 03:41 PM) <{POST_SNAPBACK}>

If your fuelpump is priming with just turning the key on, something is wrong.

not true,...that is normal for a later wiring harness and hex code... More than 2/3 of my own machines will prime when the ECU is energized with any switch, and without having to bump the starter.

BUT!...after the first cycle of a few seconds,...then the crank sensor takes over, to essentially turn the pump back on again for the same short cycle with every turn of the flywheel PAST the sensor.
Since the motor spins fast enough, the pump will run continuously. That's why you may hear the pump run a couple seconds after a shutdown...as it finishes the last pump cycle.

A simple test for pump functioning, is to rotate the flywheel clockwise after the first power-up priming. You are not having to listen against starter noise, or having to look at the filter or tank return, and you won't be draining the battery or overcycling the 1-way bearing either. If no pumping each time?...you might have a bad crank sensor or harness issue.

It's not clear from your post if the fuel connectors are still stock. The outer o-rings are not the problem -- they leak or they don't leak, and will not choke off the flow. It's the INTERNAL stuff that should be "gutted" at minimum,... and your list does not show that being done yet?

sdhow · #6 Post by **sdhow** » Wed Apr 18, 2012 4:32 am

All quick connect seals were replaced. I jumped the pump's negative to ground and the pump fires right up; fuel flows freely through the filter and into the fuel rail when the pump kicks on.

Could it be the crank position sensor? I had one of thes crap out on my E-H (same Sagem ECU system), but can't remember what the symptoms were...speakn of pulling the relay...what happens if you burn up that internal diode?

Canniboomer · #7 Post by **Canniboomer** » Wed Apr 18, 2012 6:45 am

QUOTE (sdhow @ Apr 17 2012, 09:32 PM) <{POST_SNAPBACK}>

.......I jumped the pump's negative to ground and the pump fires right up.....

hmmn beware, since that's exactly how to ruin an S-1000 ECU.... to either short the pump circuit to run the pump continuously until the fuse has to be yanked, or the pump will not switch on at all....or the ECU can go completely dead.

sdhow · #8 Post by **sdhow** » Wed Apr 18, 2012 2:20 pm

QUOTE (Canniboomer @ Apr 17 2012, 11:45 PM) <{POST_SNAPBACK}>

hmmn beware, since that's exactly how to ruin an S-1000 ECU.... to either short the pump circuit to run the pump continuously until the fuse has to be yanked, or the pump will not switch on at all....or the ECU can go completely dead.

That's IF you were to continually ground out the circuit and run on the pump for an extended period of time. I momentarily grounded the - terminal on the pump to test it for operation...this is how the circuit is intended to operate, with the ECU opening the ground and allowing the current to flow through the fuel pump. It fired up and drew fuel through the filter and into the injection line.

Canniboomer · #9 Post by **Canniboomer** » Wed Apr 18, 2012 4:24 pm

Well, I've sold dozens of replacement S-1000 ECU's over the years, and to guys that merely grounded out the pump for an instant with a nutdriver or instrument probe.
To merely test a pump itself, we always warn to unplug the pigtail first, and to use separate power. The pump is not at risk however you do it, but these ECU's get zapped all the time while guys are troubleshooting a stalling or hard-starting issue.

sdhow · #10 Post by **sdhow** » Thu Apr 19, 2012 8:33 am

Ok, now I recall what happened on the E-H with the faulty CPS. When the CPS got hot (7-10 miles), it would crap out and stall the bike. After it cooled down, it would fire right up again.

This is kinda what the quad was doing before...but now it won't refire, even after cool down. If the CPS completely crapped out, would the ground to the fuel pump be completely disrupted?