Starting problem - Detectives required *UPDATE - SUCCESS!*
I'm right at the end of my summer body off chassis resto project which has included replacing the fuel tank and lines as per earlier posts.
During the rebuild I have started to G occasionally and battery has been on trickle charge to keep it sweet.
Today I went to start it again and found that the pre-heater lamp wasn't lit when I turned the igition. My truck turns over fine and *almost* seems to fire, but just can't get there.
Searching around a few different ideas are offered on this subject, most of which are around the glow plugs and timer.
On that basis, so far I have:
- Removed the glow plugs and checked each in turn (direct feed from battery) - they all glow OK so I suspect no problem there. I will replace the plugs tomorrow anyway.
- Checked the functioning of the timer with a plug attached - again works as expected (plug glows), but still no orange indicator and truck won't start. That said I am still slightly suspcious of the unit anyway. I know that they do eventually fail and given what I have spent so far making sure that everything else is up-to-scratch, I've ordered a new timer anyway, I'll keep the old as a spare. ~
- Examined the glow plug harness - some of the cable is brittle and has cracked. No obvious shorts though and it continuity tests OK. Again I have ordered a replacement harness to elimitate future concerns.
- Tried bypassing the timer unit to heat some of the plugs directly.
- Checked the orange bulb - actually all of the bulbs in both the guages were replaced when the gagues were rebuilt (nice new bright orange needles now!) Lamp is fine.
Conclusion: I don't think the problem lies with the glow plugs!
So what can it be? My suspicion is fuel and to be honest the injection system is the part of the truck that I know least about. Some fact though:
New tank has been installed (98l plastic), tank therefore started empty, so there will be some air in the lines (all rubber feed/ return and breather hoses also replaced with SS/ PTFE).
*However* the 1st fuel filter has fuel in it, which I deduce can't mean that it is a problem with the feed from the tank (tank now has 15l in it, though doesn't register on the gague). Also, the enine was running just fine with the little fuel that was in the lines.
Is there an easy way to check for a lock, or to see whether fuel is getting through the pump?
A related question is the lift pump, which when you unscrew it seems to be free of any suction (I don't jhave anything to compare it to, but I imagine it shoudl *feel* like it is doing some work?). Are these easy to repair without having the pump out?
Any ideas or thoughts very welcome!
Hi Ben
You probably have as much knowledge about the deisel injection system as me but here goes.
I understand and always have, filled the main fuel filter with deisel to help with initail start up.
Is the fuel pre filter on the right way around and new? They usually have a flow arrow to point towards the engine.
The old 5 cyl OM617 will not self prime and needs hands priming for it to run from empty / stripped down.
The top manual hand prime part of the lift pumps do fail, i guess when your pumping air it will feel different to pumping deisel also.
The hand prime part is A000 090 88 50 and is common to nearly all MB van and truck engines, the early silver tube with a white screw top has been replaced by an all black unit but they are interchangable and are £21.40 + vat retail MBUK have stock
Other than that its check that you have all the pipes on the right way around i.e. feed and return etc and that its not dragging air in anywhere through damaged or perished pipes or poor seals etc.
Then you out of my comfort zone too.
As for the glow plug, from experience those engine in general good health will start without them, they just smoke like mad.
Even in very cold weather they start OK with one or two not working.
So i dont think it is glow plug related, but as always will stand corrected
Hope this helps
Gav
Hi
The most obvious is an airlock in the fuel system
the handpump (white knob) on the injector pump is a bit of a "joke" if you have a good battery have somebody engage the starter while you slacken the nut on the top of each injector in turn until diesel mists around the spanner the nip it tight as it is misting ..chances are after you have done three the engine will start!! albeit smoky...and lumpy but it will clear as the remaining injectors get diesel
If you cannot get misting diesel at the injectors then somewhere along the fuel system plumbing you are sucking air ....harder to trace but essential to have total plumbing integrity in order to keep fuel at the injectors ....
Hi Ben
This is the best view i have tonight...attached
Obviously you have a feed and return that is not shown too well on the second picture
The feed comes through the pre filter to the pump and then from item 206 on picture 1 back to the tank
The hoses dont have a description of from and to but the picture shows it pretty well for you to locate them.
Should be OK to suss out other than slightly diffferent plumbing with the plastic tank conversion?
Cheers
Gav
Hi - have you been able to resolve issue? Have spent considerable time on fuel lines and glow plugs this summer. At one point I was unable to start my G and ultimately found air lock in top of filter unit. Loosened banjo's and finally cleared. My priming pump does diddley skwat so found keeping as much fuel in system as poss was usually sufficient.
Good luck
Stewart
'87 300D
Frustratingly no Stuart. I did some more work on it this evening, replaced the plug and started to test but then got rained off.
Undoing the fuel return line that goes from injector 1 (front of engine) to the fuel filter though and when turned over, fuel is squirted out of the barbed connector (on the top of the filter), so something, somewher is pumping. Filter itself is also full of fuel.
I did get as far as un-tightening one of the injector feed lines as FixWin suggested and interestingly didn't observe much in the way of fuel - certainly no 'mist', unscrewing the thing entirely and it wasn't even clear that there was fuel going through.. Then it started to rain - a lot!
New harness, Glow plug relay turn up on Friday and I'll try again Sat.
Hi Stewart
Too many zeros in that ;)
Gav
Don't know what yer talkin' about?!? Looks fine to me... (didn't realise numeracy had crossed over the M1)
Grr.. second attempt.
1. Get fuel coming out of top of fuel filter bleed port using the poor hand pump.. new hand pumps ex stock from Bosch injection specialist.. or you can even get an improved brass one in the USA! If battery is poor.. bleed at injection pump too.
2. Slack off all injector nut at the injectors.. crank until they are all good and wet (with someone else cranking... look for a good squirt and then tight them on the fly (not best practice I suspect!!) and it will start as you tighten them.
3. If it is not starting if you have fuel.. then timing been messed with ?
4. The glow plug timer is driven by one glow plug.. if you remove the casing you will see one terminal on the circuit is different and feeds an "coil" shaped inductor loop. Make sure this circuit is OK.. the rest do not matter. My circuit is a bit cantankerous but as these are easy starters it does not normally become a real issue. Attached is a rough circuit of operation.
Great advice, thanks again. I'll try tonight if weather holds. Timer and harnes are being replaced for new.
Timing hasn't been mucked around with and the last time I started it a couple of weeks back it ran just fine.
As you say, AFAIK the 617 is pretty bulletproof, given fuel and compression it should run.
Like yr attached drawing...now I understand after all these years !
Swapped out the glow wiring harness and timer today, glow plug warming notification and timing now works perfectly.
Then replaced inline fuel filter and lift pump, loosened off 2 banjo bolts on top of filter and pumped until clear of air; did up banjos and the old girl fired right up.
:-) Thanks as always everyone!
Huzzah! Appreciate stress when as said the old 617 should be fairly bulletproof - I was all loaded up to go on hols this summer and wouldn't start - thankfully only a couple of hours to realise air lock in fuel filter and enough juice in battery to turn engine to pump clear (my hand pump as said is crock of ****). Not had issue with glow plug loom but have just replaced all my glow plugs (2 were dead - lots of smoke on start-up but gone now). Ah, the joys of an old car. Right, anyone for a n/a 617 drag race?
TBH, the look was just old and brittle and though it was probably OK, my policy with this project has been to replace anything that is looking tired - I think the timer was probably OK too, but I'm happy that at least with a new one it won't be something to worry about for the next 140K miles :-)
New lift pump was a good upgrade too, can't believe I put up with the old one now; fairly simple to change, but you need to take the liftpump body off the IP I found - be prepared to replace the gasket on that when you do.
The final win on this litte episode was to discover a black/ yellow lead and 2 pin connector tucked in up behind the ignition (comes off the igition loom) - quick check for the part # showed it to be a lights-on warning buzzer connector, which just needed the appropriate part (A1245450114) to work.. something I have been missing from this vehicle!
You're the man!!!!!
Click.....
Click.....
Click.....Brum ;)
JOIN THE GWOA
This website and forum are provided for the benefit of enthusiasts and owners of all Mercedes Benz off road vehicles, in particular the G Wagen. The costs of development, upkeep and provision of the site are met entirely by the annual subscriptions of club members. If you are using the site and are not a member of the G Wagen Owners Association please consider joining. You will have access to areas on the site that are not open to non members, to club trips and meetings and to technical assistance. In addition your contribution (only £25 annually) will help us maintain and develop our website for future users.
Who's new
- Jaffa_JIM_23
- Wrabstar
- GG
- KTMSCANIA22
- 280ge
Hi Chaps,
Great input as ever - Gav, thanks for the part # I'll get one in and service that anyway. Pre-filter isn't new but is on the right way around, I have a new one to fit tomorrow anyway. Pipes are new throughout earlier in the summer other than 2 clear plastic lines which are fine.
Main fuel filter has fuel in it too. I've been looking around to see if I could find a diagram that explains the plumbing of the lines, filters and pump actually since it isn't obvious to me what much of it is (for example there seem to be 3 or 4 lines into and out of the main filter.
I'll try the injector trick and report back.
Cheers,
Ben