[NPT57]

Hello All. New to the forums and really looking forward to learning a lot here. Not new to BMW’s as I have been tracking them for quite some time. I’m fixing up a new to me (2006 330i).. I’m stumped on an issue..

I have code P1429 - Electric Air Pump primary Failure

Every time I go to fill up the car - there is a TON of pressure in the tank when I open the gas cap. The pump will not fill more than a dollar of gas at a time because it clicks off due to the (what I think) pressure pushing up the gas (I see the gas coming up to over flow even though the tank is empty..).

I’ve replaced:
- Gas Cap
- Charcoal Canister
- DMTL Pump
- Purge Valve

No difference at all.

Is there a vent line that gets clogged often? All of that pressure tells me something isn’t vending properly..? Looking forward to any advice.

[gbalthrop]

Originally Posted by NPT57

... 2006 330i.. P1429 - Electric Air Pump primary Failure [NOT correct Code definition; see below]
Every time I go to fill up the car - there is a TON of pressure in the tank when I open the gas cap.[Please describe] The pump will not fill more than a dollar of gas at a time because it clicks off... Is there a vent line that gets clogged often?...

Welcome to the Forum!
1) The Code P1429 = 2A18 definition in BOTH BMW Fault Code Lookup, & Bentley:
P1429 | 2A18 | DME: DMTL, heater: activation | MSV70 | Engine electronics

The DMTL (Diagnostic Module for Tank Leakage) has THREE (3) different components: (1) Pump, (2) Valve, (3) Heater. ALL are powered by same fuse, but EACH is activated separately by DME (after engine OFF) via Ground Signal. You likely have a WIRING issue between the DME & DMTL, but I do NOT immediately see any reason that fault is related to your PRIMARY issue (Tank won't Vent when filling).

2) I'll attach Bentley ScreenPrint showing basic function of Fuel Tank "Plumbing" on your N52 to NEXT Post. I have never had reason to open my tank, or any issue with tank venting (or with DMTL), so all I can offer is my interpretation of the diagram.

I have followed E9x Forums closely for 7+ years, and there are NOT frequent posts related to vent line "clogging" or slow fill, although there have been ~ 5 or less that I have seen. NO one has reported a specific "Fix" AFAIK. Older Jag (XJ-S, etc.) systems with lines from tank to charcoal filter had frequent reports of "Whoosh" (pressure/vacuum release) when cap was opened after engine operation, but those were usually related to pump drawing "Vacuum" in tank during operation, and "2PSIG valve" in vent line NOT functioning.

I cannot remember ANY E9x reported cases of Fuel Cap "Whoosh" on opening. If YOU are experiencing either (1) release of tank pressure > ambient/ atmospheric pressure, or (2) air flow INTO tank due to "Vacuum" in tank: when fuel cap is removed, please do following:
A) Determine Conditions when that "Whoosh" is experienced: after engine operation? After sitting in sun (Fuel Vapor Pressure).
B) Determine if pressure is being (i) released FROM tank, or (ii) INTO tank, when cap is opened.

Once again, the E9x reported cases are "Pump Shutoff", presumably from faulty Vent Line (between "14" & "16" in Bentley ScreenPrint). I have NO recollection of "Whoosh" reports related to BMW E9x. To properly diagnose YOUR issue, we need answers to questions above.

ANYONE used nylon "Line Trimmer" line to clear vent tube? Any other "Fix"?
George

[gbalthrop]

Attached is Bentley ScreenPrint showing N52 Tank Plumbing and functions, as discussed in Prior Post.
George

[NPT57]

Thank you for the detailed response. I agree. I have a good feeling the P1429 code is related to a fuse/wiring issues. I’ll have to track down what fuse controls it as well as trace the wiring.

As far as the tank venting, this is my larger concern as I figure all of that tank pressure cannot be good for the fuel pump..
The tank pressure builds while driving. When I open the gas cap, it seems to vent atmospherically from the neck out of the tank. I can actually hear the internal sizzling/bubbling of the gas with the cap off.

[gbalthrop]

Originally Posted by NPT57

... [1] I have a good feeling the P1429 code is related to a fuse/wiring issues. I’ll have to track down
what fuse controls it as well as trace the wiring...
[2] The tank pressure builds while driving. When I open the gas cap, it seems to vent atmospherically from the neck out
of the tank.

1) See attached ISTA ScreenPrints, showing the DMTL wiring & Connectors between DMTL & DME. My SWAG is that you
have an issue in the Black Red wire between X1714/2 & X6041/2, OR in the White/Black wire between X6041/2 &
X60002/17 at the DME. Since ALL THREE (3) DMTL components use same fuse (F06 in E-box), and you ONLY have ONE
Fault Code (for Heater), Lack of Voltage Supply is Unlikely. There SHOULD be Battery Voltage at X1714/4 (Red/White wire)
with KL87 active: Ignition ON & DME Main Relay (KL87) active.

WHATEVER is causing "Heater" activation to fail, that is NOT related to your PRIMARY issue of lack of tank venting during Fill.

2) I can't think of any reason that PRESSURE should INCREASE in tank when engine is running. The fuel pump is
pumping fuel OUT of tank, and if there were NO vent to allow air INTO tank, a VACUUM (less pressure than ambient)
would result. If you wrap Plastic/Saran wrap around cap and remove it, that should indicate if tank pressure is MORE,
or Less, than Ambient.

The Charcoal Canister is intended to absorb fuel Vapor after engine shutdown, to LESSEN Fuel Vapor escaping into
atmosphere after engine shutdown (Evaporative Emissions). If a vehicle is parked OUTSIDE in Warm Sunlight,
the Fuel Warms, and "Vapor Pressure" (Fuel Vapor) above the liguid Fuel increases with temperature, resulting in
"Evaporative Emissions" if NOT trapped in charcoal medium.

Cap "Whoosh" has NOTHING to do with Venting while Filling. Note that Vent line is BENEATH the Fill Cap. The Cap
is NOT Vented. Pump Shutoff while attempting to Fill Tank is due to some obstruction in the Vent line between
"14" & "16" in the diagram.
George