The moment you turn the key to position 2 (before starting), the pump is powered and line should be fully pressurized. First rule out a problem with the power supply. Check the power at the connector harness located behind the left rear wheel liner. If you measure 12V in key post 2, and still no pressure, the pump likely to be dead.

 

Okay, I have more info...

The fuel pump fuse was blown...inserted new fuse and engine started briefly and ran for a few seconds at high idle...but sputtered and died again...

Fuel pressure only got up to about 20 psi...

Tried disconnecting MAF and ran a bit...but died again...

Blew the fuel pump fuse again...

where do I go from here...?...why is fuel pump blowing fuse...?

Gordon.

 

Also returning codes 0170 and 0173...Fuel Trim for each cylinder bank...whatever that means...?

Gordon.

 

Don't worry about fuel trim until you fix fuel supply issue.

 

It means there is a short on the wiring for the fuel pump or the pump is shot and creating a very high resistance.

 

It's the other way around.

 

Thanks to both of you for the quick answers...what a forum...!

Now where would I look for a short...?

And is there any way to test if the pump is good...?

Regards,

Gordon.

 

If you want to be sure why fuse is blowing, do the power consumption test. It should draw between 4-9 amps.

If your pump and fuel filter still original, replace both and upgrade the fuel lines at the same time.

 

It's 1999 ML320. Fuel pump relay is in main fuse box under the hood. K3

 

could it be a clogged filter...?

and the pump drawing extra current to overcome the flow resistance...blows fuse...?

Regards,

Gordon.

 

--Possible. That's why I asked if the fuel filter is still original or not.

--high amp draw and/or short in the wiring/harness.

 

Thanks, Merzatt...

I just performed the test and it reads just over 9 amps...about 9.5...but that is a cheap analog multimeter so error range might put it within 9 amps...

Regards,

Gordon.

 

So what does that test show...?...is the pump okay or not...?

Gordon.

 

If you can't trust tools you are using why bother. Let's say meter has 10% error. It still puts you above 9A maximum current draw. Pump blows 15A fuse so at times current draw is higher. What is fuel pressure with pump relay jumped by amp meter? How is car running?

 

Well, thanks for the "insight" Witek...

I was asking what the test means...

and FYI if the meter error is 10 percent and it is reading 9.5 amps...it means the true reading could be from 8.55 amps to 10.45 amps...

even with a 5 percent error it could be within 9 amps...

Sorry my tools aren't good enough for you...but it still does not tell me what the test means...if the value is over 9 amps then WHAT DOES THAT MEAN?

Gordon.

 

Thanks, Merzatt...

Yes the filter and pump are both original...320,000 km (200,000 mi)...I am the original owner since November '98...

I know I need a new filter and that is on its way...but not wanting to buy new pump if its still okay...dealer tech says pumps almost never fail...

I'm thinking the clogged filter is making the pump draw more current which is why it shows a bit high...but is it enough to blow a 20 amp fuse...?...doesn't seem like 9.5 should do that...? gotta be a bit more headroom than that...

So maybe I should crawl under the back wheel and look at the wiring and maybe a damaged wire or something shorting...?

Fuel pressure gets only to 20 to 25 psi...normally at 60 or so...

Regards,

Gordon.

 

But how did you do the pump amp test? Engine off, idle or full load? I am not a electrician but the amp can fluctuate depending on the need, right?

Remember, a normal pump brings the pressure to 60 immediately. Filter regulates the high limit on the pressure. So, most likely the pump is kaput. We cannot speculate what caused the death of the pump unless someone does an autopsy on it.

You must replace the filter. This is pure ignorance and your fault.
Your dealer tech does not consider the fact that a clogged filter for 100k miles could kill the pump! Now, it is much easier to replace both at the same time. If you really want to be cheap, replace the filter first and crank the engine. I would replace both.

Yes, do not forget, high currents could damage the relay, wiring, harness, soldering etc.

 

Okay I just went back and calibrated the ammeter...it's showing 18 amps...

(I was actually looking at the wrong scale the first time...)

so I guess the pump is fried...but just wondering what the reason is that a fried pump would be showing a high current draw...

Regards,

Gordon.

 

..but just wondering what the reason is that a fried pump would be showing a high current draw...

Maybe this photo will answer your question.

 

If it is not a damaged wire you really do not want to get into the fuel system twice.
It is PITA.

I would get a pump, updated lines and a filter and just do it all at once.

 

Thanks for all the help, Guys...

Now to tackle the job...does anyone have instructions for replacing pump and filter they can post here...?

Regards,

Gordon.

 

Here are the instructions for the filter and pump.

You must first check to see that you have the upgraded fuel lines to accommodate the larger filter. Remove the left rear wheel and fender liner and check to see that line #3 is in place. If so, then you only need the filter.

If not, then you must also purchase the three lines, the part numbers of which are highlighted in the pdf.

After you remove the large union nut, pay attention to the alignment notches on the pump and the tank. This is to make sure that the new pump goes back in the same exact position.

 

Thanks, 43...much appreciated...

Gordon.

 

Guys, I switched out the pump and filter today...

Took about two hours and pretty straightforward...I took out the rear 2/3 seat completely and that made things much easier...

Runs fine now...fuel pressure is a healthy 60 psi...current draw is 5 amps...

I have one nagging little question...on the new fuel filter...the two lines at the front look like they are not seated all the way...there is about a quarter inch of the nipple visible...

The back one is seated all the way down...I popped these on before I installed the filter and made sure they were all pressed in all the way...

Are those nipples on the front just longer or what...?

Would really appreciate any info...it's the Mahle filter with three lines (retrofit)...

Would hate to start tearing things apart again...

Regards,

Gordon.

 

They are long. As long as the line snapped/clicked on it and it is not leaking it is going to be fine.

 

Thanks, Noodles...that's a relief...

Yes I made sure the lines clicked into place when I put them on...there are no leaks...

and I would think that if they did not click on the fuel pressure would immediately push that line right off...

Thanks to everyone here for the much-needed help with this job...

Regards,

Gordon.

 

Just a few notes on the fuel pump job just completed...

Taking out the seat was the key...I don't see how you can even lift the carpet out without taking that seat out...

The access hatch cover is glued in with that body putty...which is horrible stuff because it is a moisture trap...wherever you have this stuff you will have rust guaranteed...mine had started to eat away around the opening so I cleaned it up a bit with some emery cloth...a shot of rust paint wouldn't hurt either...

Prying off that cover is no picnic...I first scraped off as much of that putty as I could off the outside using a sharp wood chisel about an inch wide...

Then I used a small metal drift and a hammer to get some purchase underneath the cover...and then tap with the chisel or drift all around to cut it free...

Naturally the cover ended up bent a bit...especially on its flange...I straightened this out on a bench vise by hammering on the flange and using the anvil part of the vise...just work your way right around tapping on that flange and it will come out nice and straight...

I glued it back in using GE silicone for doors and windows from the home center...excellent stuff and it won't soak up water like that body putty...

I had previously scraped off a lot of that putty from under doors and the rear hatch and there was a lot of rust under there...a lot of the door drain holes were plugged with the stuff...pretty awful...this stuff should never be used on a vehicle...

The pump is a fairly tight fit in the opening so you have to be careful that you don't bend the fuel float or the pickup...I ended up reusing my old rubber seal because I did not see the new seal in the box until it was too late...Also used the old plastic ring and it had a mark painted on to index...this way I knew when to stop tightening that thing...

The filter would have been impossible to install going by the manual directions of first attaching the lines to the pump...btw these lines may have little protective plastic bullets that you need to remove before the lines will click in place...I found this out only after trying to push them down will all my might and they would not go...duh...

I attached all three lines to the filter first and then slid the filter in place and hooked up the two lines to the pump and the one to the fuel line going to the engine...very easy...

The hardest part was the little vent hose...this has a curious little hose clamp that snaps together...you use a screwdriver to unsnap it...and then I used a small needle nose vise-grip to snap it back together...

The little plastic nuts that hold the fender liners in are real garbage...great idea to have new ones on hand because they are basically one-time use...I had noticed this previously when I changed out the CPS and had to remove the front one...

The hardest part of the whole thing was knocking the wheel off...that is always a bugger...I usually get a long 4 x 4 from the lumber pile in the barn and I slide it along the garage floor like a pile driver...after a couple of whacks like that the wheel usually comes off...never mind a rubber mallet...forget about it...

So that's basically it...not a big deal really...the carpet goes back nice and easy under the plastic pieces but you have to take that seat out...not a big deal really but that thing is heavy...must weigh over 100 lb...

Thanks again to the group for the help...couldn't have done it without you all...

Regards,

Gordon Arnaut
Ontario, Canada.

 

Glad it is all done. You saved a ton of dough. Nice work Gordon.

 

Well I spoke too soon, Guys...!

Now the fuel level gauge is not working...

I should have checked that before I buttoned everything back up...now I'm going to have to take that damn seat out again...that thing has to weigh close to 200 lb...

Any suggestions for troubleshooting...?

Regards,

Gordon.

 

You don't say how the fuel gauge is showing. Is it always empty, always full, 1/2 way, or what.

 

It's showing empty...and the caution light does not come on...although that caution light comes on when I turn the key to position 2...

 

Now comes the interesting questions Gordon:

1. Where did you buy the fuel pump?

2. What band name was it?