Hey guys, having a hard start issue and I'm at a loss as to what to check.
On a cold start the engine is rough to turn over and requires a little throttle feathering, once it turns over it misfires for a few seconds and then figures itself out. On a hot start it will crank strong and not turn over, I've been having to spray a bit of starter fluid in the intake to get it to turn over. Idles slightly rough and runs very well and strong when cruising, WOT, etc. Every single part of the fuel system and most of the ignition system has been replaced in the past 5k miles. The fuel distributor was just rebuilt by a reputable classic bmw mechanic, but he's unavailable for another 3 weeks. This problem started right after getting the car back from him, I don't think there's a chance he rebuilt incorrectly but who knows. Tested all injectors today, including cold start, all look good. Pressure regulator in the FD is clean and has fresh o-rings from the rebuild (maybe a shim is missing and its running at lower pressure?). This feels like a system pressure issue. I checked for vac leaks in all the usual places with no luck. Any and all suggestions are welcome.
UPDATE:
Problem solved, the piston for the fuel pressure regulator's o-ring was trashed and made it very difficult to get out, but I did. More info on a post down below.
Last edited by blindrooster; 01-02-2019 at 10:26 AM. Reason: problem resolved
Check the resting pressure when it's warm - sounds like your accumulator has gone bad maybe
-John
Or it could just be set a tad too lean. Have you tried to tweak the fuel mix a bit? (1/16 turn increments, it's very sensitive and that's the 2nd time I've mentioned 'sensitive' here today).
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On a side note: dirty/rusty-dusty fuel will cause similar symptoms, or worse if the fuel filter is really dirty and especially worse if the fuel filter element tears. If this happens and you're lucky - the fuel injectors won't require a 'back-flush'.
Tbd
Check fuel pump pressure and the cold,warm control pressure and then the rest and leakage test pressure-->>>>> K-Jetronic-CIS Testing---If the problem started after a repair was done-its either the repair or some item that was barely working.
Randy
hmm. The fuel filter and accumulator are both less than 5k miles old. I'm going to tune the mixture again today and possibly test the accumulator.
I attempted to set a base mixture by jumping the fuel pump relay and listen for the buzzing noise of the fuel injectors, following the faq. However I can hear a very clear buzzing noise at all times coming from around the fuel distributor, is this normal? I could not get the noise to go away by drastically leaning out the mixture or richening by turning the adjustment screw CW and CCW.
The frequency valve buzzes, maybe that's what you're hearing. The injector noise is more of a 'whistle' when fuel goes through them.
The 'base mixture' procedure is only to be performed if the base mix is way outta whack, this procedure is not used for fine-tuning the mix. If you have a running engine, just 'tweak' the mix (whichever direction it needs) a tad to see if that's all it needs. * the fuel mix adjustment is very sensitive, keep record of your adjustments, 1/16 turn increments! Let the engine 'settle' for a minute between adjustments (while tool is removed!) Note:: if there is not noticeable change with 1/16 turn increments, there may be a problem elsewhere.
*do Not flood the engine with fuel. Be aware that if the fuel mix is set way too rich, fuel will flow through the injectors until fuel 'rest pressure' drops below 40 psi, even with the fuel pump(s) 'off'.
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Side note: unless you know the condition of the fuel tank lining and the condition of the fuel in the tank(s), you won't know if the fuel filter is due for replacement. Tip :: when replacing or 'inspecting' a fuel filter, drain the inlet to a clean container to get an idea of what's in the tank(s). Let the drained fuel settle for a bit if it's an option.
I like showing this picture; rusty dusty fuel filter because bad fuel tank lining. eek:
click to enlarge
dirty-fuel-filter.jpg
Last edited by epmedia; 12-04-2018 at 04:41 PM.
Tbd
Thanks for info, I'll inspect the fuel filter.
You're welcome.
* I forgot to mention something! Very important ::
If the 3 pieces of fuel hose on the suction side of the external fuel pump are the original 'cloth braided' hoses, they are probably sucking air bubbles and seeping some fuel.. the 3 pieces of hose that I refer to, connect to the metal "Y" fitting at the suction side of the external fuel pump, two different hose sizes. If any of these hoses are letting air bubbles into the fuel system, you'll never get it tuned proper.
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The fuel tank 'Vent' hoses use the same material as the fuel 'Suction' hoses. Here's a sample of some old cloth braided vent hoses. Note the cracks in the hose linings - these cracks can be anywhere on the hose, not just the ends...
click to enlarge
bad-hoses.jpg
Last edited by epmedia; 12-04-2018 at 05:24 PM.
Tbd
Any time you jump the fuel pump socket-the correct female spade terminals, both fuel pumps will on-buzzing and the Frequency Modulation valve-buzzing in 1980-83 320i,,1977-79 just the main fuel pump is buzzing as there is no in tank fuel pump or Frequency Modulation valve.
Randy
Good tip, the PO spent over $8k getting the fuel system replaced by a reputable bmw shop who we've both noticed kind of fucked him as I've been learning new things about the car. I wouldn't put it past them to put in a new fuel pump, filter, and accumulator and use the original lines.
What about the return line on the FD? http://alexjandro.com/bmw/www.lexam....fuel-dizzy.jpg
The fuel return and fuel supply hoses under the hood are originally 'Steel' braided and are different material on the inside. I'm not sure how long these last.. My '78 steel braided lines have been ok so far, but I should consider replacing them!
When you peek at the fuel filter (or sooner) take a peek at the hoses too, every fuel supply/return/vent hose should have been replaced by now. There's a high-pressure flex hose on the fuel filter outlet you want to inspect too. There's an access cover under the back seat where you can see more fuel return, fuel supply and fuel vent hoses.
Check the http://www.realoem.com/ for pics, part numbers and some specs. *ignore the prices, they don't sell parts!
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Every original 'Cloth' braided hose on the car is beyond service life, they're used on the fuel vent system too (as shown in the pic, post #9). If you ever work with these (assuming they're original hoses), be aware that nylon "T" will probably break, so source a replacement before attempting to work on those hoses.
Tbd
What are the fuel hose sizes? Would it be easier to cut the T out with hoses attached and remove them without breaking the T? In the event the T breaks any replacements that are readily available. Need to do this on my 82.
This thread has all the info you'd ever want on it, https://www.bimmerforums.com/forum/s...lacement-guide .
Hi Robert-- Have not seen any with in tank fuel pump,,some got it some didnt.
Jumper the fuel pump socket
1.) listen too the fuel pump under the right wheel well---if its not solid buzz- skipping--this is an issue
2.) Remove the back seat, take out the inspection plate and unplug and plug in the electrical connector to in tank fuel pump---if you can't hear it or feel by vibration its working--this pump being out causes harder cold starting.
3.) There is cloth braided hoses here that tend to weep fuel smell and can be replaced as well.
Randy
Update:
I inspected the following and they all work/very new/good condition/etc:
Fuel tank: crystal clean
Fuel tank vent lines have all been replaced 11/17
I replaced the external pump (and check valve) last night as I could not find any record of it being replaced, but it looked fairly new and replacement did not change anything.
In-tank pump was replaced 11/17 and can confirm it turns on.
Checked timing, spot on.
I hooked up a pressure tester and the cold and warm control pressure were spot on, however the car loses nearly all pressure as soon as you turn the car off. It drops to about 5psi almost immediately and then drops to 0 after a couple minutes.
Further at a loss here as to what to check as I feel like every single fuel component has been inspected, replaced, rebuilt.
To recap the symptoms:
Hard cold start, misfires for a few seconds, rev it up a bit and it clears up.
Very hard hot start, usually refuses to start unless you spray starter fluid in the intake. I've resorted to wiring a button to the cold start injector to the dash as a work around. Misfires once started, rev it up a bit and it clears up.
Car always idles slightly rough, a little lumpy, misses slightly. No RPM fluctuation outside of maybe ~10rpm+- .
Runs seemingly perfect above idle, cruising, WOT.
I pulled the fuel distributor regulator out to inspect and the o ring on the outer spring part is obviously brand new, however I was unable to fish out the other end of the component, and am wondering if this is where the leak is coming from. Any suggestions on how to get this out, or anything at all is appreciated.
Last edited by blindrooster; 12-31-2018 at 11:04 AM.
RESOLVED:
Last night I was finally able to fish out the piston out of the bore for the fuel pressure regulator in the distributor. The o-ring on the end is thrashed and I'm confident this is the issue. For anyone who has problems getting their piston out in the future, this is what I did to get it out: Every time I got a grip on it and pulled it out a bit it would slide back in a bit because it's under vacuum, cracking open a fuel line a bit relieved this issue. Then it was binding up on bits of destroyed o-ring so I fished bits out with a pick and a small mirror to see what I was doing. Then I used to small pieces of wire bent in an acute angle, slid them in opposing each other, and pulled them out together to act like a grappling hook on the piston, this did the trick.
Awesome, good luck. These are the o-rings I ordered from the o ring store,
3 x 2mm X 7mm FKM (Viton) O-Ring Black (V2.00X007) $0.60 3 x 2mm X 4mm V75 Metric FKM O-ring Black (V2.00X004) $1.11 9 x AS568-008 V75 FKM (Viton, Fluorocarbon) 75 Duro O-Rings (V75008)
Note that you only need two, the piston style changed at some point so I just ordered them both without thinking about it. More info here, https://www.bimmerforums.com/forum/s...ulator-O-rings
Hello, I’m having a similar issue and am looking to replace this o-ring along with my accumulator in hopes that if my accumulator doesn’t solve the issue, an O-ring will. I was curious if there is any way you would be able to point out which piston you have to pull out in order to reach this oring? I understand that it’ll take some digging to reach the oring, I’m just very unfamiliar with this fuel system and am unsure where the fuel pressure regulator bite is located at in the fuel distributor. Also was it just this one o ring that solved your problem? Thanks in advance!
- - - Updated - - -
Just clicked on your link lol. Awesome help on here. Thanks everyone!
Man, I really look like a newb with all of the posting on here lol, after reading through the diy I’m Just left with one question, by taking out the piston and replacing the orings and then re assembling with a new, is anything going to have to be re adjusted? (Assuming that my fuel mixture is already set where it’s supposed to be?
Only if the fuel mix was previously adjusted to 'compensate' for a bad o-ring on the pressure regulator, would you have to tweak the fuel mix after repairs - leaner fuel (CCW) - tiny 1/16 turn adjustment increments. Otherwise, you should not have to adjust the fuel mix. And don't flood the engine with fuel... be aware what's happening while doing tests.
Last edited by epmedia; 01-21-2019 at 03:52 AM.
Tbd
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