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E300TD unusual starting, plus air bubbles

16K views 81 replies 6 participants last post by  Al_Savage 
#1 · (Edited)
So. This is the 98 E300, and I'm really curious about how this car starts.

When car is cold, after glow plug warm up, the car starts right away. The engine turns over at most, 3 turns before it starts.

When the car is warmed up, and I try to start it, it takes maybe 5-8 turns before it catches and turns on. There is significant difference between the two, and I'm wondering if it's due to the air bubbles present in fuel lines.

I say air bubbles, but I can't be sure. When car is running, I don't see anything. Nothing. When I put a flashlight right up to fuel lines, I see something moving. But it's so small and so rare that I'm not sure it's air bubbles or just the distortion of the lights. It's well within margin of error, and user error too.

Steps I've taken: replaced the overflow valve, pre-filter and main filter in front.

Steps I'm planning on doing: replace all fuel lines and tank strainer filter. Would that fix the potential air bubbles and the unusual hot starting issue?

Kajtek? :D This was your car, after all.
 
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#2 ·
That made me wonder as well as it always happen like that. Maybe not 5-8 turns, but 1-2 for sure.
Can't make solid explanation, but quite possible is that on hot engine the remaining fuel in the injectors boils and make miniature vapor lock?
I replaced the tubings at above 200k, or 6-7 years so looking at your chart they might wear out.
Check for bubbles at high idle, but if the tubings stay clear, no bubbles and no drip, I wold not rush the job.
Than it was like $60 cost and less than 1 hr labor, so not a big deal.
I have new fuel filter forya if you did not replace it yet.
 
#4 ·
Well, my theory is that when the car is cold, the air bubbles are gone, so there is pure fuel in the line, allowing for quicker start.

However, when warm, that means there are more bubbles in the line, so it takes a bit more fuel until it catches on. I disabled the EGR, so it can't be that.

Just my theory. Kajtek's theory is another possibility. But then again, most diesels start easier when engine is hot, so in theory my E300 should start even faster. But I have the opposite. Friend of mine has a old Chevy S10 diesel, and he has lengthy cold start problems, but it turns on almost instantly when hot.

Would installing a fuel filter inline fix the air bubbles? According to folks in Pelican forums, the inline filter catches bubbles and filters fuel, so double duty and they say car starts quicker too.

And the fuel lines are 6-7 years old according to Kajtek, and looking at them, they're really yellow....so it's time to replace them anyway. But good point, I will check them.

And really? Less than $60 for all lines, plus o rings? When I price them online, they come out to $100+. I should talk to the dealer then. But then you included a whole bunch of lines when I bought the car, so there is less for me to buy.

I already had tank strainer and shift interlock on order when I made this post, but another one wouldn't go remiss. Now I have to deal with a somewhat serious transmission leak, the shift interlock on the diesel finally gave away. This weekend I will replace it...and track down the mysterious exhaust rattle that's only present at idle.
 
#5 · (Edited)
Bare in mind that engine for start takes fuel from high pressure lines.
I would estimate that amount of fuel in injectors, high pressure lines is enough to run the engine for several seconds, so whatever happens on hard start happens on high pressure side. Even if air bubble exist, they don't matter much at 2-3000 psi.
Other possibility is software glitch. The injection pump is electronically controlled, so if program does not open fuel for a second, that makes hard start.
Your rear muffler was repaired in the past, so the rattle will be hard to fix. I tried and gave up.
With your connections you might find cheap replacement.
Parts prices went up, but still most of tubings sell for $10
http://www.autohausaz.com/search/pr...ar=1998&cid=fuel@fuel&gid=6352@Fuel Hose/Line
Don't forget SOV oring, prefilter oring.
Check the leak lines as well.
 
#6 ·
prefilter ring, already replaced it.

SOV ring, will order it.

Pretty sure it isn't software glitch, because I've modified the stock map just to turn off EGR. Everything else is identical to how it was.

leak lineS???

Cold start


Hot start


If you notice, the battery drain is significant between cold start and hot start. Starter?
 
#8 ·
Maybe, but I do have the feeling that the cold/hot starts are distinctly different.

At least with my Dodge Ram, it starts the same exact way. Cold, hot, wet, doesn't matter. But then again, it's not a diesel, so thats not an accurate comparison.

You mentioned leak lines. What leak lines?
 
#9 ·
The 5mm black hoses that come down from injectors.
All 3 of my Powerstrokes takes several turns to fire up. That might be due to fact that design is using compressed motor oil to power the fuel injection, so you have more potential pressure dropping points.
Than thinking more about harder hot start, I tend to highlight the control idea.
There is no reason why hot injector doesn't fire, but it will after cooling down other than lack of engagement.
 
#10 ·
When it rains, it pours.

I got the infamous window regulator problem in the diesel. Both of the rear windows dropped, and refuse to go back up.

I've been trying to track down a mysterious MPG drop. I went from 600 miles a tank to barely clearing 400 miles. I've been trying not to think about the possible cause for the mpg to drop.

So far, I have to...

replace all fuel lines
inspect fuel leak lines
replace the tank strainer
replace the shift interlock lever
replace both window regulator
investigate the mpg drop
investigate the exhaust rattle
and finally, change the oil.

Oy vey.
 
#11 ·
I've been trying to figure how how to get MORE than 400mi to a tank when everything seems to be running perfectly. I'm now thinking the torque converter is not locking. It behaves very differently on the highway than my 2001 in terms of throttle position vs rpm. Next time I'm at my indy I'll get them to check trans codes.
 
#13 ·
lol, I wonder who is that? :p

I did check the codes. Nothing. EGR is permanently deactivated, and I've disconnected the vacuum line to the EGR. I've also tested the EGR valve to see if it's completely closed -- as in there is no crud preventing it to completely close. There was some, and I managed to scrape enough that it became waterproof.

Today I replaced the tank strainer, both motor mounts and all fuel lines.

The old tank strainer had lots of crud in it. When I put my fingers in the tank, there was at least 1" of crud all around. I managed to scrape some out, but I think I might have to take out the tank sometimes later.

Motor mount managed to smooth out some vibrations, but there was some. The interesting thing was -- on the old motor mount, when I put in drive and gave gas, the engine barely moved. On the new one, it rocked back and forth depending on the gas, but it was a noticeable reduction in the cabin. I'll chalk that as an improvement.

Replaced all fuel lines. Then...starting the car was hell. 50% diesel in the tank, and the car tilted forward (that was fun :D) and cranking -- no start at all. Diesel would enter the line, and as soon as I stopped cranking, it would retreat, leaving the lines empty.

After half hour of cranking and burning out 3 batteries, I got pissed and used spare parts to fabricate an airtight gas tank seal, and then pressurized it to 40 psi with compressed air.

Then I cranked. 10 seconds later, car started.

Now, the problem: air bubbles! :(

From what I can discern, there are 3 lines that have bubbles. Bubble from main filter to SOV, then from SOV to to the highlighted area (I don't know what that is. It doesn't look like its SOV), then back to the filter.

This bubble is present in both idle and revving. Idle is smooth, however. Drives fine too. Sometimes the car rocks a bit, but then smooths out after 2-3 seconds.

I haven't replaced the SOV O ring, but the problem is, I don't know where it is! According to EPC, the O ring (#32) is right behind the SOV (#29), but if I have to remove it to replace the O ring, then I also have to replace the gasket (#41). What gives? Where is it?

But the bubbles start at the filter, and not the SOV. What are my options in this case?
 

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#17 ·
I will be watching this thread as i have the same starting condition with my 97 e300.Its not a problem as it starts ok but it definitely starts more quickly cold than it does hot.Pretty much the opposite of what one expects from a diesel.In the last few years i have had a diesel Jetta, a 91 300d 2.5 an 87 300 tdt and years of working on marine diesels and have to say this is the first i have seen that starts quicker cold than hot! How can that be on a compression ignition engine? Maybe someone can enlighten me. Don
 
#19 ·
Couple more thoughts. I think the crud on the strainer is from 1990's and early 2000's when we had high-sulfur diesel fuel.
In last 6 years I had to clean strainers on 2 of my Ford Trucks and they had very fine mesh clogged with varnish-like stuff. No visible accumulation of dirt, just glued holes in the mesh. Meaning ULSD makes no crud, but varnishes.
Than the air bubbles might come from old fuel hoses.
The car has them between tank and steel pipe and than at firewall and they are likely 18 years old.
Replace those at least on suction line.
 
#22 ·
I think I might have found one of the possible causes for the 33% mpg loss....

IP delivery valve seals!

Yesterday I was treated to the sight of a decently sized diesel puddle on the garage floor.

Inspected it today and after 3x cleaning and observing the leaking while car was running.... have confirmed it to be a serious leak from cyl #6 delivery valve.

Might explain why?
 

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#23 ·
Leak is a leak, but you've been saying about loosing about 6 gallons of fuel from each tank fill.
That amount of dumped fuel in few weeks would make you easy to find in whole LA, just following the wet asphalt and the rear of the car would drip as well.
Do a baby powder testing.
 
#24 ·
That's just the thing, I've had the wet IP and the under pan was wet for the longest time, just no drips or anything. Yesterday I saw a puddle that was bigger than the engine (it was visible from the sides) and there was a clear smell of diesel before I got close. I estimate it was close to 1/10th of the tank capacity, if not more.

Here's the weird thing though, that puddle showed up when car was off. Today when the car was running, I could visibly see the diesel leak out, there was a lot coming out...so I doubt baby power is needed. There's a catch can underneath it now, we'll see how much it leaks out by tomorrow.

You're correct though, that won't explain the missing 6 gallons, but it's a start, right?
 
#25 ·
Replaced the SOV o ring and all delivery valve o ring and washers, but as I was buttoning things back up, the return fuel line from the IP to the fuel filter broke off.

Bugger.

Local MB does not stock any diesel fuel lines, so I have to special order and have it by tuesday/wend....and since I have two dead cars in the shop (my ML and E300) that means I have to ride my motorcycle home in this heat.

Double bugger.
 
#27 ·
I think they do...they have to.

But the local MB did have the serpentine belt for a CLK63 AMG in stock when I ordered it....lol. They also had air suspension compressors and ABC pumps in stock as well.

Guess that shows what's the money maker in this area is.

On the upshot, hopefully the parts for both E and ML will arrive by tuesday, which means I can have both cars on the road soon. Especially the ML, since I still haven't managed to start it yet.
 
#28 ·
40 PSI? FORTY!?

That's tank-destroying pressure. I would think a reasonable max for a fuel tank might be four or five PSI. I'm completely nonplussed that you didn't break a seam in the tank. I bet when you look at the tank next time you change the sender, that it's deformed.

----------------

I've only owned mine for seven months and one oil change, but I have noticed that it lights off immediately cold and about three times as long hot. Hot, it cranks maybe two seconds -- much longer than any other hot diesel I've owned. Hell, in my '82 Chev. G30 6.2l diesel I could tap the ignition switch to Start and have it running. That used to amuse my friends.

One theory I've had is that it does not actually open the SOV until the oil pressure comes up. But that's really a WAG. But there's no denying that it takes several more revolutions of the crankshaft to fire mine up when hot.

My GP light is also on for two seconds on a hot start. I wait for it go go out. It does seem to make a difference.
 
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