Another no start issue
 

Hello all. Well, I was hoping to write an intro before having car troubles but not the case. I’m returning to the forum with my recently acquired 87 911 with 148k miles. I owned my first 87 911 cab for 7 years from 2007-14. This one is a coupe and has had a recent fuel tank replacement by PO, professionally installed. New fuel pump also was professionally installed after original one died about 2 weeks ago. Bought and drove car from OH to AR (also about 2 weeks ago) without a hiccup (except strong fuel smell when tank was filled to the brim—I think this is a separate issue but am open to suggestions). Last Sunday I took it out for a spirited drive, and it ran great. Stopped for a meal and came back out to head home. Car started and then sputtered and died. Tried several times to start it, and it would sputter some and die. Switched DME and just cranked with no sputter or anything. Had to flatbed the car home.

Here is what I’ve tried after consulting Bentley and several threads:

—checked and confirmed good battery connections
—confirmed spark with spare spark plug
—confirmed a fuel delivery issue by car starting with starter fluid and then immediately dying.
—removed DME relay and jumpered 30 and 87b to check functioning of fuel pump. I can hear a low thump (a little hard to describe) when tested but does not sound like what others describe when fuel pump is running (I just don’t remember what the fuel pump sounds like). After a short period, the fuel pump becomes very hot to the touch when jumpered.

So where do I go next? Bentley says check fuel pump ground wire (brown wire) for continuity to ground but unsure how to do that. Could the fuel pump be bad, and how could I confirm this? Am I missing anything obvious?

Thanks in advance.



Sent from my iPhone using Tapatalk

Low thump? Should be a soft hum. You might get a fuel pressure gauge to connect to the port back on the driver side fuel rail. The fuel smell when full is the nice thing about owning a cab! Gonna sound dumb but are you sure there's gas in it? The sending unit could be wrong.

Thanks for your response. Yeah, I remember that advantage of cabs... the only advantage maybe?!?! Haha

It has gas, confirmed by gauge and mileage driven.

Definitely not a low hum with fuel pump.

Ok, will look into checking fuel pressure.


Sent from my iPhone using Tapatalk

Another bit of data: it seems pump doesn’t respond the same with the key on as it does when i jumper 30 and 87b. So no thump when I turn the key on.


Sent from my iPhone using Tapatalk

The fuel pump will not run with the key just turned on. It has to be in start/cranking mode. Then it's hard to hear it over the cranking engine.

You jump 30 and 87A to get the fuel pump to run. Might be different on an 87 but the SC's use 30 and 87A.

Thanks for confirming the fuel pump only runs while cranking.

In the pic of Bentley there is no 87a, only an 87b (sorry if that pic is inverted).

Attachment 10503


Sent from my iPhone using Tapatalk

My '85 3.2 fuel pump runs when ignition is ON. (Doesn't make sense that pump would only run when engine is cranking if cranking means turning the motor over to start it.)

Thumb means the pump has likely seized

If you jumper 30 to 87 and the pump doesn't run, but you hear a thump, it could be that something jammed up the impeller in the fuel pump. That would also explain the pump getting hot.

Agree, the pump has likely seized. It should not be getting particularly hot.

Then someone tuned it to do so. Mine runs for a few seconds when I turn the key on then turns off. The reason the pump doesn't run with key on, ignition off is safety. The pump runs while the engine is cranking.

exactly. It does so to build up fuelpressure.

would the replacement tank happen to be a Dansk, i have had several problems with
there tanks taking out new pumps.
i always use a pre pump filter now when using a new Dansk tank

came to my mind... vacuum breather free?

That makes good sense Nick.

I try not to do that too often and I think I hit my limit for the day. :D

Back on this issue. If the fuel pump was locked up causing heat, you should have popped the fuse. I would think the motor trying to turn the locked pump would draw more amperage (hence the heat) and pop the fuse. Without being there I can't say for sure but it doesn't seem like the pump is seized since the fuse didn't blow.

You can also jack up the front, drop off the skid plate, and check voltage at the fuel pump when the relay is jumpered (per instructions by others). If you don't see 12 volts, then their is an electrical problem.
If you do see 12 volts, you can pull the end of the fuel line to the fuel filter in the engine bay, and put it in a jar. Then jumper the relay again and see if you get fuel delivered by the pump.
If you have voltage but no fuel, the pump is failed in some way.

Thanks for all the comments, y’all. I’ll have to call the business in OH that installed the tank. From the receipt, it cost $475—would that make it a Dansk?

Also, I agree it should have blown the fuse if locked up, but the fuse is still good. I did check voltage at pump and got zero voltage, but I’m not sure I did it correctly. I jumpered 30-87b and put multimeter in both connections of pump—is that how to check voltage correctly (sorry, electricity confounds me)?

@porschyard, I’d like to learn more about your pre-pump filter. Could you offer where you source your filter and maybe a pic of your finished product?


Sent from my iPhone using Tapatalk