Rmon New Reader
11/24/13 1:01 p.m.

Hey guys, some of you may have already seen my thread about fuel problems I've been having with my E28, but I figured I'd start a thread.

So, we (my brother and I) bought the car for $1200 a few weekends ago. its a 1985 535i with 189,300 on the odometer, which quit working an undetermined number of miles ago. We've estimated it's more or less at 200k right now.

Here she is on the side of the road, waiting for a tow:

And at home:

The history of the car is as follows: The original owner had it until May 2013. He dumped $20k (!) into the thing from 2011 to 2013 and apparently still had problems. So he sold it to someone as a project car. This owner, the one we bought it from, drove the car down the street, saw smoke, parked it, and put it up for sale. I'm not sure he knew what "project car" meant.

Good Things

  • Painted in 2010, looks gorgeous from 6ft, and not bad up close

  • All new front suspension (arms, bushings, ball joints, etc)

  • New P/S system

  • Receipts indicate both fuel pumps were replaced, but fuel problems persist

  • Interior is not bad for a nearly 30y/o car

  • New TRX Michelin Tires, these are the remakes of the original TRX's. They're $200 a pop from coker tire

  • I'm pretty sure the entire braking system has been redone, they feel amazing and the components look new.

  • Brand new B&B exhaust, cost the PO $1k

  • Half of the electrics work

Bad Things

  • Half of the electrics work: Speedo, Tach, temp don't work, The HVAC fan doesnt seem to be getting power, Sunroof motor turns but doesn't do anything, The windows are hilariously slow, The head rest motors make one hell of a racket but don't do anything, and I'm sure there's more I'm forgetting.

  • There is an odd steering squeak when you turn the wheel. Like every quarter turn, it squeaks, but only when the steering is loaded. It won't do it with the car standing still.

  • The car has a serious fuel issue. (This is what I had posted about - E28 Fuel Issues). It sputters under load, but sometimes will accelerate fine. Rarely will it have issues when revving in neutral.

  • The in-line fuel pump is ridiculously loud.

It may have a lot of problems, but damn this car is fun to drive, even at only 10mph! I'll try and keep this thread updated, maybe you guys can help me with some of the problems.

oldtin UltraDork
11/24/13 1:18 p.m.

I still miss mine. One of the best built cars I've ever owned. May sound odd, but check your grounds. Mine would sputter and run like crap in heavy rain - wouldn't reset until you disconnected battery - reconnect and ran fine - combination of water soaked 02 sensor (water inside the wire insulation and a crusty battery ground.

I thought ferrari owners were the only ones that would actually shell out for the TRXs. The odometer issue is a broken gear. $20 fix, window regulators have gummed up old grease. A lot of these issues are pretty well documented on mye28.com. Mostly is sounds like it just needs some time and attention and maybe a few new switches.

sometimes the DME in these go a little wonky - the solder joints inside start breaking causing intermittent issues. If you're handy with a pencil soldering iron you can reflow the joints.

Rmon New Reader
11/24/13 1:33 p.m.

So, Our first order of business was to get the car driveable, which means sorting out the fuel issue. Our first step was to replace the fuel filter, because why not? We were in for a surprise.


Surely, this was the problem. The old filter was difficult to blow through, unlike the new one. The car started and idled better than it had, but the fuel pump was still very loud (remember, this is a fairly new Bosch OEM pump). The car drove great for about 3 minutes, but then sputtered to a halt. It wouldn't rev past idle, so it took us about 10min to drive half a mile home.

So, last night I did a fuel pressure test, and got a reading of 35psi at idle -- about 10 psi below what I should be getting. When I revved the engine, the pressure went down (I though it was supposed to go up a few psi?), and disconnecting the FPR vacuum line didn't do anything at all.

At this point, we're suspecting debris/residue in the gas tank. Now, the original owner had the fuel tank replaced, which makes me think it wouldn't already be rusting inside. However, this is the only theory we can think of that makes sense. It would also explain all the dirt in the fuel filter we pulled off.

Next weekend, I plan to drain the gas, pull the in-tank pump, and possibly drop the tank in order to get it cleaned out or at least see if there's anything in there that's causing a clog.

Here's some video of the problem - E28 Fuel Issue Video

oldtin UltraDork
11/24/13 1:46 p.m.

that's nasty. may they replaced the tank with an even rustier one.

Rmon New Reader
11/24/13 1:50 p.m.

In reply to oldtin:

What's funny is that it doesn't have a drain plug on the bottom like it should. Makes me wonder if it's stock.

I would think the fact that it ran well for a few minutes with the new filter would support rusty gas. It was getting fresh gas until the new filter got clogged again and then the issue came back.

bluej GRM+ Memberand Dork
11/24/13 2:44 p.m.

Sounds like you're on the path to tracking it down. Definitely jealous of your ride! Have you visually inspected all parts of the feed lines? If you pinch the return hose aft of the fpr, can you get the pressure to rise?

I think we all agree the dirty gas is the root issue, just need to track down all the impacts.

bearmtnmartin GRM+ Memberand HalfDork
11/24/13 6:45 p.m.

Plugged filter will cause the fuel pump to be noisy as well. Why is the fuel in the bucket black? It looks more like oil. You can cut the filter open to see what is trapped in the pleats to see what you are dealing with.

Rmon New Reader
11/24/13 6:48 p.m.

In reply to bearmtnmartin:

There was some oil in the bottom of the bucket, which is why it looks so dark.

DILYSI Dave MegaDork
11/24/13 11:13 p.m.
  1. Drop tank. Empty it. Flush it. Several times.
  2. Reinstall. Put in fresh gas.
  3. Run fuel pump with filter disconnected until what comes out is clean.
  4. New filter.
  5. Run fuel pump with return hose disconnected from tank until what comes out is clean.
  6. Send injectors out for service.
sethmeister4 Dork
11/27/13 10:35 a.m.

I just got done with this same issue on my old 280Z! A freshly cleaned tank and all is good now! Good luck!

Rmon New Reader
11/27/13 5:48 p.m.

So, we got the fuel tank out.

It's bad...

The fuel coming out.

The inside of the tank.

So obviously the tank is very rusty. Does this tank seem too far gone to try and use sealer on? POR-15 sells a fuel tank sealer kit that looks pretty good, but I'm not sure if it would work on a tank this bad.

Tyler H
Tyler H GRM+ Memberand SuperDork
11/29/13 7:56 a.m.

That's actually not that bad on the rusty tank spectrum. I used that Eastwood 4-step kit on my MR2 tank with great results.

Does the M30 have a lumpy, almost-miss at idle? Because if it doesn't something's wrong.

While you're doing all this, replace all of the rubber fuel hose and worm drive camps, all the check valves, etc. That gunk is in everything. Then send your injectors out to be cleaned.

Unless you have records of regular valve adjustments, look up the 'cam-side' method. (Adjust the valve clearance at the cam side of the rocker insted of the valve side, as the eccentrics wear into the valve stem with deferred maintenance.)

DILYSI Dave MegaDork
12/1/13 9:28 a.m.

Agreed - that doesn't seem too bad to me. I think I'd send it out to be dipped (just because it's cheap and DIY'ing a tank cleaning is a PITA), then repaint the outside and reinstall. Absent holes, I wouldn't mess with the sealers.

EDIT - and yes - I have to think that's your problem. Disgusting.

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