Engine problems - dirty fuel

Discussion in 'Engine' started by Charles Morgan, Dec 24, 2014.

  1. Charles Morgan

    Charles Morgan MB Club Veteran

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    Well, it's not a Merc, but it's the season of goodwill to all men, and I hope that includes old BMWs.

    My newly acquired 1984 BMW M535i E28 is super, the engine pulls like a train, but after some years of non-use when the fuel tank was filled the neck had corroded and it cracked. Supplying dealer sent me a new replacement fuel tank almost by return of post, from ECP, but no problems there.

    I had the car recovered to a local garage who are normally sensible but have had a lot of staff turnover of late. The tank was changed and re-filled with the petrol from the old tank (it was almost full). From that moment on it was gutless, hitting the throttle would make no difference, and then it would surge then almost stall. They removed the fuel filter, which of course was full of rust, put in a new one and after testing it said it was fine.

    When I picked it up it was fine for a mile then just became hopeless, I kangarooed across town never getting above 25mph even on a dual carriageway. I got out of the car with motion sickness (to which I have become prone). It will idle, but above that will almost die.

    I'm not taking it back to the garage to do as I no longer trust them - refilling without checking on the state of the fuel is just beyond belief. My idea is to get the fuel sucked out completely by one of those wrong fuelling specialists, replace the fuel filter, check the injectors and have the fuel lines flushed out.

    Any thoughts on plan of action? It is such a pain to have to sort out what was a lovely runner when I'd rather be getting on with the Merc W114.
     
    Last edited: Dec 24, 2014
  2. Giantvanman

    Giantvanman Hardcore MB Enthusiast

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    Personally, I would empty the tank and steam clean it on the basis that any rust from the neck may well have gone into the tank as well. Then I would refuel and use the new fuel as cleaner along with some Millers BUT I would disconnect any fuel return pipe, directing it into a separate container. The next step would new filter (sacrificial) and lastly injectors if the engine doesn't run smoothly after sacrificial filter is replaced.
     
    Last edited: Dec 24, 2014
  3. John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    First off I'd drain the tank, add fresh fuel, replace the fuel filter again (no harm splitting open the old filter & inspecting it, listen to the fuel pump as well) and take it for spin.
     
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  4. John Jones Jr

    John Jones Jr Hardcore MB Enthusiast

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    One other thing, not fuel related. Inspect the oil feed to the camshaft, common for blockages to occur of the oil feed pipe and devouring the cam lobes.
     
  5. Red C220

    Red C220 Hardcore MB Enthusiast

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    I do hope you get this sorted in the 80's and early 90's I really wanted an M535i Sport. They were awesome.

    I also wanted a Capri 2.8i Special though!

    What I got was a 1986 Fiesta XR2 as I couldn't afford the insurance on the others.
     
  6. OP
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    Charles Morgan

    Charles Morgan MB Club Veteran

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    Well, it is (was) awesome until the fuel tank. The car is totally original and un-molested. You can pick one up for a lot less than a Capri too. Given the price differential between the E28 M5 and the M535i (which is a dead ringer and frankly more usable) I would buy now!
     
  7. Red C220

    Red C220 Hardcore MB Enthusiast

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    I'm still trying to convince Jay to sell me his Blue 560 SEC. I miss mine.
     
  8. grober

    grober MB Club Veteran

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    The main thing to check is the primary fuel pressure in the fuel rail- if that isn't correct the system is never going to run correctly. All the previous suggestions are valid approaches. One possible scenario is that most tank outlets have filters If there's a layer of rust in there then just driving down the road was enough to shake any tank deposits up sufficient to clog the tank outlet or fuel filter again . If you are lucky then the filter will have done its job and the fuel system downstream of it will be fine- if not then its a total fuel system stripdown and clean. One approach to the previous suggested would be rig up a small temporary tank to feed the fuel pump and another new filter [ to be on the safe side] and see if that cures the problem- that might tell you if its only the tank thats effected Any fiddling with high pressure petrol fuel systems is hazardous so exercise great care and discard/wash out any clothes that get soaked in petrol?
    ps always a good idea to have a petrol fire extinguisher to hand as well
     
    Last edited: Dec 24, 2014
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  9. grober

    grober MB Club Veteran

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    Last edited: Dec 25, 2014
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  10. trapperjohn

    trapperjohn MB Club Veteran

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    Hope you get this sorted very soon Charles. You know you will, its just the bloody angst no one needs.
     
  11. OP
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    Charles Morgan

    Charles Morgan MB Club Veteran

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    Got it in one Mr B - I can live with the problems that the cars cause me, it's the ones the mechanics add to the list that really hack me off!

    I think you are right Graeme - there are two types of in-tank pump, and I suspect that is at the root of it.
     
  12. grober

    grober MB Club Veteran

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  13. Bellow

    Bellow MB Club Veteran

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    Tie a magnet to a length of string and go fishing in the tank for the offending loose rust! (or some variation on the theme).
    If you have to remove the tank to clean it, the old biker's trick is to add some gravel and shake to knock the loose bits of rust off. Easier with a two gallon tank than a ten gallon one though.
     
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  14. Bellow

    Bellow MB Club Veteran

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    Rethinking this, it is more likely the sediment being stirred up and readmitted to the tank than rust having broken free.
    The fuel would be fine if you could safely filter it. The first filter is probably continually choking and will do as long as the sediment remains in suspension.
    If it were mine I'd use my Pela suction pump (pure vacuum - no part of the pump comes into contact with the fuel) avoiding allowing the tube to draw from the floor of the tank, decanting into a Jerry can each time it fills until only a few litres in the tank remain. Then if the drain plug can be freed I'd drop the remaining fuel via that and then flush through with some clean fuel. If the fuel was undisturbed prior, there'd be chance the sediment was close to the drain plug exit. Hopefully, it could all be washed through.
    With another receptacle for the fuel I'd pour from the Jerry into it using a funnel with a stocking (or tights) stretched over its widest point to filter any remaining sediment and then refill the tank with it giving it a second straining while doing it.
    Thereafter, I'd be prepared to replace the car's own fuel filter a few times over until I was happy all the sediment had gone.

    I'd avoid using any electrical pump for risk of spark, not be tempted at any point to use the tanks own pump (lest it be uncovered of fuel and spark) and crucially, remember that an empty tank is infinitely more dangerous than a full one.
     
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  15. Bellow

    Bellow MB Club Veteran

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    More thinking on this... Given the tank has so recently been installed removing it should be relatively straightforward with all fixings being fresh.
    Having drained the bulk of the fuel (I'd still go Pela - or just syphon (bead that is a tight fit to the syphon tube bore attached with a string running the length of the tube inside when yanked through should commence the syphon)) leaving the last few litres which can then be swilled around with the tank removed and poured quickly from the tank's neck. Some clean fuel for another rinse and that would be the surest way of ensuring all sediment is removed from the tank. After that, if the removed fuel can be considered clean enough (after straining) then jug that back in and keep an eye on the car's own fuel filters for a little while and immediately if any of the symptoms return. Moderate fuel starvation during high speed running may not cause a misfire but could be enough to damage pistons or exhaust valves.
     
  16. OP
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    Charles Morgan

    Charles Morgan MB Club Veteran

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    I think that's the best way (and what a great way to start syphoning!). I'm going to get the car to a local recommended BMW specialist with experience of the model as well.
     
  17. E55BOF

    E55BOF MB Club Veteran

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    "what a great way to start syphoning". +1000 for that. No more mouthful of fuel....
     
  18. Bellow

    Bellow MB Club Veteran

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    Physically swilling and rinsing will be the most effective method I think.


    If you can't find a bead, a bit of knotted rag will work. Stout bit of string required as it takes a committed to tug to pull through rapidly enough to start the syphon. Sure beats spitting petrol!
     
  19. OP
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    Charles Morgan

    Charles Morgan MB Club Veteran

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    As the car had been standing for a good few weeks I'd thought I'd check out how difficult it will be to remove the fuel filter - it is difficult and I think not safe on a driveway on axle stands.

    The filter is after the inline fuel pump in the fuel system and there is also an in-tank fuel pump. Rather than fiddle around in difficult conditions I'm going to book it into a local specialist with good feedback and let them sort it out.
     
  20. OP
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    Charles Morgan

    Charles Morgan MB Club Veteran

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    I looked at getting a siphon pump to help get some of the petrol out - no garage wants 70l of fuel to deal with, and found this video on the internet. It works, no need for sucking, pumping, just do as the chap shows.

    [YOUTUBE]xpHqraOdMDs[/YOUTUBE]
     

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