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Old 07-17-2008, 01:51 PM   #1 (permalink)
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Question death of a fuel pump

In days-of-old, external fuel pumps were gone when the diaphram deteriorated and fuel would not enter gas lines; engine made a distinct sound of bogging-out; pump leaked. Dead and gone.

Q: Some have said I have a bad fuel pump (probably caused by improperly storing car with low tank and no stablil) in my '98 Z3, 1.9 because my car intermittently stalls out while starting, stopping and driving - it backfires too. If it's the fuel pump, how could I have gone through two tanks of gas. When is the pump dead?

Can I test the fuel pump from the top of the vehicle w/o special tools? My pump is in the tank which needs to be dropped to access. Hence,
can I disconnect a line and turn car over to see rate of flow (30 oz in 30 seconds)

Can someone tell me where the fuel regaltor is on March built '98 Z. The manual I have does not show picture of my engine. It show a regulator at the end of the fuel rail- I don't see a regulator where shown. Can a fuel reg be tested w/o special tool?

To date I have changed the fuel filter, air filter, checked top side vacuum lines, and cleaned plugs. I may need to check plugs again as I have driven 500 miles under fault symptoms.
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Old 07-19-2008, 12:08 AM   #2 (permalink)
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to answer your Q: a fuel pump to be considered in good working order should be able to sustain a pressure of 3.5 bar and a flow rate of 2.25litres/ min. If ur pump even if operational doesn't conform to those parameters, it is deemed defective and needs to be replaced.

reason: you will cannot expect the injectors to work properly unless the above are met.

translated to the symptoms that the car displays... a car with defective fuel pressure will not be able to atomize the fuel pushed through the injectors... thus, u will either hv droplets of fuel... or no fuel into the combustion chambers. Because the car cannot "digest"/combust whole droplets; or have nothing to combust at all... then u have the probs u speak of.

There is a port on the injection rail that allows you to test for injection pressure. If u do not wish to spend on special tools, then maybe use your imagination and make a deal with the shops that abound around u :-)

disconnect a line... no. flow rate alone doesn't mean anything. fuel pressure is everything.

TIP: a fuel regulator hardly ever goes bad... unless of course, it isnt functional bcz the vacuum line is disconnected or cracked. it's a better idea to check for cracks or leaks in your intake vacuum lines.
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Old 07-19-2008, 11:28 AM   #3 (permalink)
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Talking

Hi Darkhorse. Glad to meet you. I've read some of your other posts. Great contributions to this forum.

Ok -- I don't want to use my imagination, but where is the port you are talking about on a 1.9. Is it on topside of fuel rail; back or front? Does in look like a cap on a valve stem? Can any good mechanic run a pressure test?

The car has decent pick-up for a 1.9. I especially think is accellerates very well in 4th and 5th gear (higher end driving). This is why I am not inclined to think the fuel pump is causing my problems. I've also put over 500 miles on the car since the symptoms started. I've used two small bottles of Techron with each fill; and a bottle of dry gas; also using top tier fuel. Gas mileage however is fair (25-26mpg on freeway).

Do I have to remove the intake to check all the vacuum connects? Would vacuum leaks only cause problems intermittently or would they be there all the time?

When you get a chance, I would welcome your feedback.
Ted
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Old 07-27-2008, 11:32 PM   #4 (permalink)
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Hey Ted, am sorry I wasn't able to reply to your post in a timely manner.

I read through the most recent post/s you made including this one and I will agree that you can probably rule out the fuel pump as at fault.

"...but where is the port you are talking about on a 1.9. Is it on topside of fuel rail; back or front? Does in look like a cap on a valve stem?" <<< YUP! that one.

I put in my 2 cents worth in reply to your most recent posts and we'll take it on from there;-)

Cheers.
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Old 07-28-2008, 10:59 PM   #5 (permalink)
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Gratz!
I had a flashback from a year ago. I remembered the idle changing (less smooth). I thought I was being OCD at the time cuz my car always purred.
Perhaps I've spent too much time on the bad fuel/too much storage. Perhaps my problem started last summer???
I intend on code help. Is Autozone worth the trip?
TED
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Old 08-20-2008, 12:46 PM   #6 (permalink)
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I need to know if any of you have heard about a fuel pump going out due to having subwoofers in the trunk of a 1985 635 csi. My customer said that Irvine BMW told him that the vibrations in the trunk would crack and break the fuel pump. If any of you have heard such a thing, PLEASE LET ME KNOW ASAP!!

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Old 08-20-2008, 03:41 PM   #7 (permalink)
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Quote:
Originally Posted by Audio_Fonix View Post
I need to know if any of you have heard about a fuel pump going out due to having subwoofers in the trunk of a 1985 635 csi. My customer said that Irvine BMW told him that the vibrations in the trunk would crack and break the fuel pump. If any of you have heard such a thing, PLEASE LET ME KNOW ASAP!!

sales@audiofonix.com
it's possible... low frequency sound is currently being worked on/experimented for warfare use... u can take ur insights from that.
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