Diesel Duties

[rennfarher]

I figured I should make a thread about this car and maybe get some answers!



I bought a 95 525TDS here in the states. Pretty cool! Got a loooong options list and several cool options are on it. But I’ve wanted a diesel for a long time and I figured if I can get the lord chassis and a diesel, then it’s a match made in heaven!

Started off with some maintenance, main injector had a leak, and the car would constantly overboost and hit fuel cut. Bought a new injector off eBay. When replacing it, I ordered the bmw injector line tool, but that was a waste of money as it just started stripping the line nut. Just ended up using a 17mm wrench. Then when unplugging it, it pulled the connector off the sensor and left it stuck in the harness. Then trying to pull the rest of the connector out of the harness, it took the female connector and ripped it out of the harness. What a shitshow. Thankfully working at the dealership I had quick access to new pins with pigtails and rewired the harness. Turns out someone put the wrong injector in. There’s 2 different styles with 2 different plugs, and someone just shoved the wrong plug into the harness. New injector in and harness repaired and no more leak!






I also looked into all the vacuum lines (they were a mess) and found that there wasn’t a line to the wastegate, and there was a bunch of capped lines that just dead ended? Cleaned those up and ran lines from the reference port to the MAP sensor and wastegate





Also did a general inspection of the car and did an oil change while I was in there, diesel oil gets black faaaaast and it’s gets daaaaark.

General consensus was good overall. Oil drain hose clamp was loose and hanging, moved that back up and tightened. Rear sway bar endlink was broken so I replaced them. Most interesting of all, is that it’s a medium case but uses an e30 style diff and subframe. 4 bolt input, not rear cage on the subframe. The rear cover is the rear subframe mount. Interesting move for a car that has more torque than an m50 and is a LATE MODEL (01/95 build date) but still using such antiquated technology. Also the bottom of the radiator support bolts on to support and give room for the intercooler as it sits below the radiator! Interesting solution to that problem.








Now as far as all the maintenance I’ve done, the car has loved it but it still acts weird at times. It doesn’t like to hard start. It’ll crank and crank and crank and eventually start while the ambient temps are cool, but here in TX while it’s hot the car just would not hot start AT ALL. Very annoying, thankfully not the only e34 I have. So how does one go about fixing this? What’s the issue? I’ve read the pump is the issue, and I’ve read the chain has stretched and caused the pump to ever so slightly move out of time. I’d like to argue the pump is likely the cause but I’m not sure. I’ve started putting fuel additives in like Hot Shots Secret Diesel Extreme, and it has helped with the hard starts so it leads me again to the pump.


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[zubbie]

Interesting to see a diesel here but you are unlikely to get much advice seeing as they are so rare in NA. I'd be tempted to cross post on one of the UK bimmer forums where diesels rule.. GL

[Sriufke]

Welcome to bf.c man. It's weird to see someone with an M51 engine in the states since US market was never blessed with such engines in the first place. Only e28s with m21s made to US and some Vixen motorhomes along with liconcoln mk4 coupes which were also fitted with m21 engines.
Anyways...
Your distributor plunger inside the injection pump is most likely toast warranting the hot no-start condition.
About the cold start...have you changed the glowplugs? If not. Do that first. The glow plug relay is unlikely since these don't really go bad. The glow plug indicator in the cluster works, and it's not flashing?
Also confirm that your in-tank pump is operating. It's a low pressure pump with supplies the high pressure injection pump with fuel.
Also if your fuel level drops below 15-20 liters it likes to begin drawing air in the lines instead of fuel due to poor fuel pick-up design.

[circuit.heart]

Also if your fuel level drops below 15-20 liters it likes to begin drawing air in the lines instead of fuel due to poor fuel pick-up design.

Is the diesel's low-pressure fuel pump/pickup design different from the gasoline cars? I have done >1G lateral with less than 5gal (~20L) left in the tank and managed to avoid fuel starvation.

[Sriufke]

Is the diesel's low-pressure fuel pump/pickup design different from the gasoline cars? I have done >1G lateral with less than 5gal (~20L) left in the tank and managed to avoid fuel starvation.

Yeah. It's a different animal. Diesel version equips a very low pressure in-tank pump which generates about 0.3bar of pressure and has additional pick up tube above the actual pump for either easier fuel flow or for high pressure injection pump "deadheading" purposes. It's a pretty stupid design.

[Broccoli]

You are right about the timing chains stretching causing hot start issues. You can check and set the pumps static timing it is .95mm new and .90mm lift for engine with over 20k. If that doesn't solve the issue you can buy a "hot start fix" chip for the dme online as its a common issue. Cool car btw!