At some point the car slowly started to take longer and longer to start, eventually it began timing out and occasionally it would take multiple start attempts. I figured out that my tank pump was at times clearly not coming on, likely due to age, it seemed to get hot when exposed and would work after cooling off. I replaced that hoping it would solve all my starting issues, but the long crank remained. I then found fuel puddled on my fuel filter. Not surprising since I found lots of shoddy dealer work after the AEM install. Investigation of various fuel lines revealed several micro leaks and or loose crimp clamps and hose end cracks. After making temporary repairs of all the suspect joints, the car has been consistently starting within what seems like a reasonable amount of cranking. I have yet to replace every little hose and clamp, so I may have more tiny air leaks, but at this point I think I'm in the clear with this issue. The lousy dealer work actually helped me find this issue, go figure. The car has a new battery, glow plug controller, and no known glow plug issues based on codes and a resistance check at the harness.

I just wanted to pass along my findings for anyone else with long diesel crank times.

 

well, I though i finally made good progress towards this fix but it failed the problem is back. All i now is that it seems to start well when cold and sometimes takes a long time when warm. Today it timed out without starting, but then started right away on the second attempt.

Any thoughts? I was thinking of sourcing a check valve for the fuel line and putting it somewhere in the line in front of the tank to see if fuel is flowing back into the tank. Not sure what engine temp would have to do with that, but...

Could a failing crank position sensor do this without giving me a code?

 

what holds the fuel pressure between the tank and the high-pressure pump when the car is turned off? I assume there is a check valve somewhere?

 

I don't usually suggest this because its rarely, actually the problem but have you tried a new fuel cap? Its supposed to let air in, but not out. That might be the problem in this case.

Also, my CDI has about 200k miles on the original starter. It seems to be cranking slow. I'm thinking that I might have this issue in a few weeks/months/years myself, if the starter motor doesn't fail completely before then. I don't see how it could last much longer. How does yours sound when you turn the key? Does it sound like its dragging?

 

Does the fuel cap act as a check valve by keeping the tank form bleeding pressure?

The starter is strong and cranks quickly, I don't think that is an issue, battery is new as well.

Right now, this issue is clearly affected by heat. The car consistently starts well when it's cold. But if I say drive to the store or gas station, I will have a hard time starting it, sometimes the ignition times out and it will not start at all until something cools down. Yesterday I replaced the crank position sensor since I have read that it can cause this same issue. Not fully tested yet, will be doing that this morning. I also have a camshaft position sensor on order since it is possible for that to exhibit similar behavior. Both sensors can apparently begin to fail and not produce codes, so since they are inexpensive, I am eliminating them as an issue.

Today, if my testing shows i still have a problem, I will fit a check valve prior to the fuel filter with a temporary setup. If that solves it, then i'll see about possibly the gas cap being bad. Not sure if there is a way I can test that?

Thanks for your thoughts!

 

The fuel cap is designed to allow air to fill the void in the tank, as the fuel is used but not allow the fuel vapor to escape. Otherwise, the fuel use would create a vacuum and lock up the the fuel system. So in a sense, it is sort-of a check valve. I'm not saying it's "definitely" your problem; in fact, it's probably not but its worth a shot.

 

right. It's on the list now.

After replacing the crankshaft sensor, things have been good. Not perfect, a couple of slightly longer crank times than what I would consider normal. But two days of testing and no super long cranks or start failures. I almost got stuck at the dealer getting the sensor, it failed to start 3 times, then I let it sit for about 20 minutes before it finally fired on the 4th try.

I'll get the camshaft sensor in later this week as a preventative measure if nothing else. No other fuel leaks that I can find and I have looked at all the hose connections except for at the injectors. Hopefully I can get those all inspected soon.

Thanks for the help

 

The car would not start in below freezing temps after crank sensor replacement. High pressure side readings were around 130 bar while cranking with no start, been told this is too low but I haven't seen it in writing.

I found today that my air filters were overly clogged, this spring was super windy here with tons of dust daily, I'm thinking it caused early clogging. I left one off while replacing the camshaft sensor and starting became great! Unfortunately, I did two things at once, replacing the sensor and unrestricting the air. I'm betting on the air since the filters were as bad as I've seen. Maybe it was really throwing off the starting profile? Not sure that explains why it would not start when cold though, maybe it was the cam sensor causing that? tomorrow morning's below freezing start will be a good test. If I have time, I may put the old sensor back as a test.

fuel pressure readings at idle are unchanged after the filters and sensor (260 bar), start happens quickly but the pressure looks to be below 200 bar when it fires, then moves up to 260. Still searching for documentation on required starting pressure range and normal idle pressure.

As it sits:
New battery this year
New glow plug controller this year
New fuel pump relay
New in tank fuel pump (old one was intermittent)
New fuel filter (due anyways)
New fuel lines to and from filter (old, cracked and leaking at the connections)
New crank sensor (unknown condition but cheap enough to eliminate as an issue or future issue)
New camshaft sensor (unknown condition but cheap enough to eliminate as an issue or future issue)
New air filters (due for replacement, very dirty, clogged even, more than i have seen in the past ever)
All fuel lines and return lines inspected for leaks
New quantity control valve (bought thinking it was a pressure regulator)
Engine cranking RPM found to be around 160 when warm (too low as far as I know)
No codes

Limited testing today has shown excellent starting, but this has tricked me before. Will update after further testing.

Thanks for all the help

 

Ambient temp of 21 F this morning. It started nicely, again fired at about 130 bar. I hope to get graph of a warm start today as well.




warm start:

 

My wife reported a long crank time yesterday during a warm start. I've been shown a star system image that says the rail pressure should be 292 - 332 bar at idle. So, it seems that I am for sure dealing with a low-pressure issue. The quantity control valve readings were out of spec, so that will be replaced today and re-checked to see if the readings change at all. The pressure regulator reading is steady but always right at or just below the bottom of the range shown on the star system and my scanner so, there may be an issue with that unit.

 

Quantity control valve replaced today, only tested at the house, no real world driving. Inconclusive results thus far but it seems to be behaving on par with the old unit. Pressure regulator readings appear to be a bit higher now though, remaining within the specified range for all idle tests. However, Rail pressure is unchanged from before.

I did notice though that after some starts it will idle at 800 rpm and after other starts it will stay at 700 rpm. Not sure why that is happening, it idles well at both speeds. I'm also not sure which speed is the correct idle for this car?

 

Looking back through the data, my cranking rpm tonight was consistently around 160 rpm with a warm engine. Previous starts show lower when totally cold and 1round 170 when hot. Looks like ir should be around 200 RPM normally. I have a new battery as of feruary, I'm wondering if this could be caused by something other than a weak starter?

After the QTY valve replacement, it took a bit to start since air got into the fuel system, so that's why I was able to record steady cranking RPM.

173,000 miles and the starter is original as far as I know.

 

After re-evaluating the starter RPM and considering its age, I swapped for a remanufactured Bosch unit. The car now starts like a new car!

I feel like this whole issue was a combination of several factors that had the car on the low end of the starting threshold, so it would sometimes be hard to start but not always. My starting RPMs are now higher but only by about 10 - 15 rpms. But I believe it gets to max rpm faster. So, I think I'm getting higher pump pressures more quickly. That would in theory lead to a better misting of the fuel more quickly as well. Along with more rapid cylinder heat buildup, this made a big difference.

My lessons learned is to start with the most fundamental items first and that a scanner that can read live data is extremely useful! Also, many people on the internet will throw around numbers as hard facts but never provide documentation to back them up. Always search for documented proof from the manufacturer before determining that the numbers you are seeing are not within spec.

As it sits, starts like a new car:

New battery this past February
New glow plug controller this year
New fuel pump relay (old one proven to be bad)
New in tank fuel pump (original one was intermittent, seemingly common thermal failure noted by others)
New fuel filter (due anyways)
New fuel lines to and from filter (old, cracked and leaking at the connections)
New crank sensor (unknown condition but cheap enough to eliminate as an issue or future issue)
New camshaft sensor (unknown condition but cheap enough to eliminate as an issue or future issue)
New air filters (due for replacement, very dirty, clogged even, more than i have seen in the past ever)
All fuel lines and return lines inspected for leaks
New quantity control valve (bought thinking it was a pressure regulator, did not seem to have an effect)
Replaced starter with remanufactured Bosch unit from eEuroparts. (made a huge difference compared to the original unit that was 13 years old)

 

Going to note here that often times one can clean and grease up the starter and have it back to spinning like new. I've done this with many starters.

 

I don't doubt it. Not worth the risk or time for me personally since mine was so old. Peace of mind to just swap it out and increase the reliability even if it didn't solve my original issue.

I would have liked to try that though if it was less of a pain to swap out. Good suggestion for those that can't wait for a starter to show up or are on a tight budget.

 

Follow up.

I ended up having some starting issues again some number of months after the starter went in. Mostly long crank times. I ended up doing leak by tests on the injectors and after seeing lots of fuel pushing to the return system on most injectors, I replaced them all. No starting issues since, car starts great all the time and I noticed better fuel economy. I used Merc branded injectors from FCP Euro since they were on clearance at the time. Definitely worth doing a leak by test if you have a lot of miles your injectors.

I think most of the items I replaced were contributing to the longer crank times or no starts, so I've concluded it was worth it to swap out all of things around the same time. All parts were original as far as I know.