280GE Starting Problem Following Fuel Tank Replacement
I have a 1989 280GE LWB which, until 3 weks ago, would start at the turn of the key, first time, every time. I had to have the petrol tank repaired and after re-fitting yesterday, I can't get the engine to run. It fires and almost bites, but then drops out again.
I have checked fuel lines at distribution manifold and am getting plenty fuel there (disconnected supply/return lines and turned over, plenty fuel in jar)! So looks like fuel pump is OK. I cleaned plugs (which were pretty clean anyway). It's almost as if it was permanently flooding?
Can anyone suggest next diagnostic steps - I am guessing I may have air locks between distribution manifold and injectors but don't want to go too deep just yet.
Any suggestions will be greatly appreciated.
have you recharged your battery, after 3 weeks in this weather it may not be giving a strong enough spark to the plugs?
Check that you have not contaminated the fuel filter or accumulator(on the chassis leg) with crumbled rubber from inside the hoses you disconnected when you removed the fuel tank.....make sure the electrical connections are correct.the fuel pump relay activates the seventh injector cold start system (like a choke)
I appreciate that you have checked fuel supply at the distributor but just as a process of elimination is the fuel pump operating?
Easy way to check. Turn ignition on and off with the drivers door open and listen for it running. It should operate for 2 - 3 seconds each time you turn the ignition on.
Having removed the tank I assume you have drained the system so it may take a while for it to get back up to operating pressure. So try turning the ignition on and off maybe 10+ times in quick succession before you attempt to start it.
Just because you have fuel doesn’t mean you have filled the accumulator, fuel filter, distributor etc. Jetronic needs to be up to pressure before it works correctly
It's almost as if it was permanently flooding?
Could suggest there is no spark, check for that, then check your ditributor and rotar arm. Going on the assumption every thing was fine before the fuel tank change over and nothing else being touched, the only probable cause could be wrongly fitted fule line at the fuel sender unit, dirt accumulated in the fine qauze filter housed in the injector body to where the fuel-in hose is connected, remove the 17mm brass like nut and the small conical filter should be housed in there.
Checking fuel from the fuel-in hose to the injector body is not sufficient enough a check, put your thumb across the hose and fuel should be squirting out under some pressure. Use eye goggles to protect them from fuel hitting your eyes.
These are dangerous tests' to be doing. Have an assistant present and fire extinguisher at hand!
Regards,
So, new fuel filter (still no joy). Plenty spark (re-charged battery), engine still fires and runs for approx 2 seconds. I can hear fuel pump run for 2-3 seconds when I click ignition on initially - and I can turn on/off several times before the pump evenually doesn't run at initial switch on - presumably system pressured up OK. I have to leave standing for several hours for pressure in system to dissipate before I can repeat the initial running of pump.
I tried bridging terminals 30 and 87 on fuelpump relay - which according to an earlier entry in this topic, should have reulted in the fuel pump running continuously - but it did not! Can anyone advise if this is a relay problem or do I need a new fuel pump? I'm more mechanical than electrical bias so don't fully follow what function the relay is performing.
Further thoughts appreciated.
If your fuel pump does not run withe the relay connections 30 and 87 bridged then from that it is obvious there is no permanent live feed to the relay, hence the vehicle cuts off two seconds after start up. Whilst, you are cranking the engine, live is supplied by the starter circuit through the relay. I will need to look up the wiring cicuit to help you further and come back to you.
In the mean time, with a volt meter check to see if there is a live feed at terminal 87 of the relay with the ignition switched on. If you have a probe which can supply power as well, that would be great you could easily apply the power from the probe to apply at terminal 87, which would resolve this issue for you.
The relay could be at fault, but I am bugged down by the fault arising from when you canged your fuel tank, it is something done during this work, that somthing has been distrubed.
The relay acts as a rev limiter, it acts like a switch to your fuel pump supplied with heavy wire as it is supplied heavier current, but uses low current wiring and current to act as a fast acting switch to prvent contact arching enabling you to have a long life switch other wise the switch would ordinarily burn out. This helps in designing the use of less heavy duty cabling over a longer circuit line reducing the or making efficient use of power.
I will be back.
Regards.
Rakesh,
A friend is lending me the sort of probe you describe, so I can carry out further checks at the weekend (I work away during week which means this diagnostic is taking ages). A new relay is only about £3.00 so I'll pick one up in case.
I still have a feeling that I may have a partial fuel blockage (accumulator?), but don't want to start pulling all of the hoses/pipwrok out just yet - it's pretty rusty under there! Or could it be a partial short in wiring - I may have disturbed something during pump removal from tank.
Thanks again for your support, it's much appreciated. I was at a point of getting ready to sell, but the more I work on the Wagen, the more I am enjoying it - so will be keeping!
Cheers for now,
Simon.
Hi Simon, I think a new relay is about £80 so just make sure you are looking at the right thing. I have been through similar problems, but on a 230 which is slightly different and would recommend checking all the wires for continuity - a broken earth wire might have enough contact to run the pump for a few secs then break the circuit.
NB don't be tempted to put 12volts direct to the pump without disconnecting the wires back to the relay or you will definately blow the relay - done that so that's how I know.
I am now somewhat embarassed. I was jumering the WRONG relay - so back to locate correct one (drivers side above fuse box??) this weekend and try again. Shan't buy a new one just yet - if that's the price!
Earth may be an issue, I did have to re-terminate a bundle of earth wires following a slight accident during tank removal - corroded terminals on main earth boss at rear end. I'll re-check my crimps etc.
Apologies to you all. As I said before, not good on electrics!
Simon.
Just being studying the wiring diagram for the 280 GE; try checking on fuse no: 12 for good contact, remove and clean the tapper contacts. If the fuse has deep cravis where the fuse holder has dug into the fuse contact, then renew the fuse.
To try and achieve any more depends upon starting and doing the very basics in its proper order. It might be just worth to get a sparky check the system out for you.
Just waiting on some feed back from you.
Regards.
All,
Just to say thanks for all of your help and suggestions. Cutting a long story (and most of the past few weekends) short, it turns out to be an earth fault. After many checks on relay, pump, new filter, etc. etc., I jumpered an earth wire from battery negative directly to fuel pump and when ignition tried, engine started first time. Removing the temp. earth cause the engine to begin to miss; re-attaching, smooth as it has been always.
I also note that the rear lights are quite dim!!
Next weekend I'll weld a new earth boss to chassis and re-terminate all of the earths at the back end of the Wagen.
Best to all,
SimonW.
Congrats, isn't it a nice feeling when it's back working.
Just a tip on welding - you will burn off the underseal on the inside of the chassis leaving it prone to corrosion, might be better to drill and tap - a metric fine thread should hold ok.
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Many thanks to all of you.
I'll check out the suggestions to date and let you know how I get on.