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Mercedes Benz 280GE
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Discussion Starter #1
my 280ge won't start again. It cranks but just won't go through. I've already changed fuel pumps (Bosch) twice in the last few months. My mechanic suspects the fuel pump relay switch or the auxilliary valve. The G is now just lying in my parking. I miss it. Now I have to use my Lex GS to go to work. Any opinion which part of the G I have to I should also check aside from what I mentioned above?
 

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280 ges 1989
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321 Posts
The simplest test of the fuel pump –without pressure gauges is to undo one of the 6 pipes from the fuel distributor to the injectors and turn the ignition on –fuel should come out – be careful its high pressure. Does it fire at all or just keep turning with no sign of life? If you are getting fuel to the right place the next logical thing would be no spark – check the sparking by removing a plug lead, plug in an old spark plug and attach it to something grounded – see if it sparks when turning the engine over – be careful removing the spark plug caps – use sparkplug pliers to turn and pull the cap – pulling on the rubber part will destroy the lead – very costly. If you have no spark it could be the coil or the ignition module. Also check out inside of the distributor cap and the rotor arm.

To check out the injection you really need fuel pressure gauges – the Bosch mechanical system is all about differing pressures – all the aux air valve does is to put more air in during warm up so I would not have thought it would prevent the engine from firing at all. The engine manual explains it all very well – a good investment.

The Manual shows it all – if don’t have one you should get one – they are available from www.4x4abc.com and also to members of www.gwoa.co.uk

Good luck
 

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2000 G500
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1980 LWB 280GE
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Just my opinion......

I'd try easy stuff first.

Pull a spark plug wire and insert a spare plug in the open end. Ground the body of the plug, crank the engine and look for spark. If you get spark you can forget about the ignition system. If not, look at stuff like ballast resistors, distributor cap, TDC pickup, spark box, coil, etc, in roughly that order.

Pull the "baffle plate safety switch" wire off the fuel meter body as shown by the yellow arrow in the first picture here:
http://www.clubgwagen.com/gtech.php?pageTitle=G-Tech Article&sid=item&tid=32

Then turn on the key and see if you hear the fuel pump run - if you do, the fuel pump and relay are fine. Then pull the black metal inlet air pipe off and depress the air meter baffle plate. If you hear the injectors start spraying, then the fuel meter and injectors are delivering fuel.

All these tests will take a total of about 5 minutes to narrow the source of the problem. It's worth doing some general tests to let the machine guide you to the right areas before launching into detailed evaluations of a single component.

All that said, I agree the fuel pump relay is high on the list of likely suspects if it's a fuel problem. I've always been glead my early 280GE doesn't have that goofy relay. Mine just has a regular 5-pin relay that looks just like the ones that I use to run my headlights and such. It's nice security to have those automatic spares on board at all times. I even swapped one in during an investigation once.

As far as the "auxiliary valve" being a problem, I presume he's talking about the auxiliary AIR valve? If so, then it would either start normally when cold and not idle after it was warmed up (stuck open) or require you to hold the gas pedal down a little in order to run when it was cold (stuck closed). It's difficult to imagine the aux air valve causing a "no start" condition.

-Dave
 

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Mercedes Benz 280GE
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Discussion Starter #8
just installed a new fuel pump relay (cost me US$120) and still there's nothing. Nothing at all. Would you guys think my G just died a natural death?
 

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2000 G500 NMLE
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aggarao - 3/22/2005 1:16 AM

just installed a new fuel pump relay (cost me US$120) and still there's nothing. Nothing at all. Would you guys think my G just died a natural death?
Have you tried direct wiring the fuel pump to see if it will run?
 

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1980 LWB 280GE
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Maybe a wire broke back at the fuel pump. They get brittle with age and maybe all that fuel pump changing, plus a little driving, broke the wire.

What were the outcomes of the tests?

-Dave G.
 

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Mercedes Benz 280GE
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Discussion Starter #11
my mechanic and electrician are looking at the problem this weekend. thay said if they can't find the source of the problem, they'll probably re-wire the whole fuel system electricals. i'll let you know about the results. by the way, the break lights also stopped working.
 

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aggarao - 3/23/2005 6:36 AM

my mechanic and electrician are looking at the problem this weekend. thay said if they can't find the source of the problem, they'll probably re-wire the whole fuel system electricals. i'll let you know about the results. by the way, the break lights also stopped working.
A good place to start would be some of the ground (earth) points at the back of the truck.
 

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1980 LWB 280GE
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DING DING DING We Have A Winner!

I always forget about this part because I eliminated it from my truck.

Your mention of the lights is key.

See this article:
http://www.clubgwagen.com/gtech.php?pageTitle=G-Tech Article&sid=item&tid=19

Find the two plastic connectors between the brake pedal box and the inner fender under teh hodd as shown in the second picture. Unplug and re-connect both of those connectors and see if things don't start working perfectly.

My problem was with brake lights. After having to fiddle with those connectors twice in a month, I replaced tehm with GM WeatherPac connectors. No problems in the 3 years since.

Good luck!

-Dave G.
 

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Mercedes Benz 280GE
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Discussion Starter #14
that have been checked already. all grounds have already been checked, cleaned and tightened.
by the way, when we opened and removed the cover for the fuel pump, it was full of dried mud and sand. do you think that has anything to do with the wires?
 

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1980 LWB 280GE
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aggarao - 3/23/2005 10:12 AM
....do you think that has anything to do with the wires?
I guess I'm not sure... That's what testing is about, checking where you have power and where you don't under what conditions. If someone could tell you what the problem is over the internet, you probably would have found it yourself already. [:)]

It's going to take some methodical investigation starting from the beginning. We never did hear how your tests for ignition vs fuel problems came out.

The best thing about problems like this is that terrific forehead slap when you find out what the real problem was, and how NOW all the symptoms make perfect sense. [:)]

Good luck!

I sure hope it doesn't come to re-wiring the truck, but if it does, you can avoid wire problems in the future if you use wire that is "full length tinned". This wire is tin-plated throughout it's entire length inside the insulation. That way the copper wire doesn't corrode and get brittle.

I like Ancor wire:
http://www.ancorproducts.com/Products/Home.html

All the best,

-Dave G.
 

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Mercedes Benz 280GE
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Discussion Starter #16
the tests for the fuel pump, fuel pump relay, starter, spark plugs and injectors were perfectly working. the problem was on the wires (see attached photo) going to fuel pump. the contact points were corroded.
my 280 ge is on the road again. thanks guys.
 

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aggarao - 3/28/2005 8:05 AM

the tests for the fuel pump, fuel pump relay, starter, spark plugs and injectors were perfectly working. the problem was on the wires (see attached photo) going to fuel pump. the contact points were corroded.
my 280 ge is on the road again. thanks guys.
This is quite common in older G's. Sometimes I think that Bosch hired all of their personnel from Lucas.

Glad it's back on the road!
 

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92 300E 172,000 miles 1985 280GE
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Guest said:
I always forget about this part because I eliminated it from my truck.

Your mention of the lights is key.

See this article:
clubgwagen | G-Tech Article

Find the two plastic connectors between the brake pedal box and the inner fender under teh hodd as shown in the second picture. Unplug and re-connect both of those connectors and see if things don't start working perfectly.

My problem was with brake lights. After having to fiddle with those connectors twice in a month, I replaced tehm with GM WeatherPac connectors. No problems in the 3 years since.

Good luck!

-Dave G.
Oh my god, this thread saved me from SOOoo much frustration. Had the same problem with the G, except the brake lights did work, but having exhausted all other possibilities I decided it was easy enough to try unplugging and replugging those wires, and poof, the truck runs! I think we'll we doing that GM conversion very soon. Thank you for the info! I would have never thought to look at those wires.
 
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