280GE fuel issue
Hi,
I have just bought a 280GE and it has a running issue. The previous owner has fitted a new fuel filter and fuel pump.
I can get it to run fine for a short period by pouring fuel into the metering head flap area, but when that runs outs the G cuts out.
#1 The fuel pump buzzes for 2-3 seconds when you turn the key (as it should)
#2 There is a click from the dash which I believe is the relay
#3 I appear to have fuel to the metering head
#4 When I cracked off the injector feed pipes from the metering head they all show fuel.
I have now checked the pump and it also buzzes during engine cranking, which leads me to believe this is not the problem.
Given that it runs on fuel directly applied I put this down to a fuel supply issue. Can anyone advise on how to test/what to look for?
Hi The Bosch Jetronic mechanical fuel system as fitted to your G' is complex..go into your search engine and enter as described above and study for a bit..the high failure item is the cold start regulator...but if it ran before the fuel pump and filter was changed and you are getting fuel to the "seventh injector" could be that one of the many vacuum pipes is perforated or detached robbing the air sensor of suction...not easy to sort out without awareness of the system.....the pump will run as you turn the key on and stop after 3or4 seconds...when you turn to start it wll run continuously once the engine has started.rpm should indicate 1000/1200 rpm at cold start slowly reducing to 700rpm when hot...at every hot start engine should rev to 1000/1200revs for 5 to 6 seconds and drop to 700revs at idle ....hope this helps rgds Peter
sounds like the relay
Hi Did you look at the accumulator ( close to the electric fuel pump in front of the fuel tank... could be part of the problem....if the pump is loud enough to hear from inside the car it could be starved of petrol.(kinked or collapsed hoses) when you say it runs when your pour petrol into the air sensor ( a fitting under the metal pipe that goes to the airfilter with a floating plate in it that should be closed and only moves when inductiion air is being drawn in) does it just rev out and stop with lots of black smoke?.....
sorry I was under the impression that you had by passed the relay and had flow, another possibility is that the pick up in the tank is blocked or partially blocked, tanks the age of your car are invariably corroded usually from the top down.
It's very easy to check whether you have sufficeient flow rate from the pump. Disconnect the reyrn line from the fuel distributor and connect a flexible hose to the threaded section. Start the pump and it should deliver 1L in 30s. (from memory) Obviously pump it into a can.
Replace the filter first, then the fuel pick up in the tank, the accumulator last if you don't acheive the flow rate.
As you claim, when fuel is poured into the plenium chamber it gets the engine started, for the moment we can rule aside an ignition fault. Concentrating on the fuel problem, you have indicated fuel to reach the injectors but that can be mis-leading. You ideally need to check for fuel pressure. The K-jetronic and similar genre of injection systems have an operating pressure of around 3 bars.
Check the fuel flow rate as per Roly's describtion, you should be able to collect approx. 1 litre of fuel per 30 seconds of runing the fuel pump by bridging the fuel pump relay. FURTHER MORE, and most imortantly, try and put your thumb across the disconnected fuel feed pipe to get a feel of any fuel pressure. If you are able to stop the fuel flow without difficulty, the fuel pump should be suspected. If the fuel presents some resistance even to a point that blocking the fuel off with your thumb pressure is not enough to block fuel flow at the end of the fuel hose, you have a healthy pump. You will need to turn your attentions to the metering head.
From where you disconnected the fuel feed pipe, in the metering body should be fine gauze filter, remove and clean as necessary.
Ideally you need fuel pressure gauge to diagnose faults at the metering head. This a piece of kit that cost some £300.00. Most independant garage do not ordnarily carry this kit, so I do not supose you will. Here, all I can say is pass the job on the a professional fuel injection specialist, i.e. Bosch agent garage to do the prognosis fo you. Faults could lay with fuel pressure regulator, fuel metering head or some one tampered with the fuel mixture screw. Ohh, note also, when attempting to crank the engine, with the air filter cover to the metering head removed, does the air mass sensor plate fluctuate to travel downwards or is it static? With ignition turned on by an assistant, as the fuel pump primes its self quickly check to see by pressing down on the air sensor plate if any resistance is offered. There should be resistance. A side line point in your comments earlier, bridging the fuel piump relay only primes the fuel pump, you will not get the engine to start just by bridging the relay and cranking the engine , the relay has to be connect as that is part of the ignition ciruit.
Let me know with more feed back as to your findings.
Good luck.
Hi the tarry substance is generated when petrol is allowed to evaporate..it becomes petroleum residue..to flush the tank first remove the fuel guage sender....use heating oil (2 gallons)in the bottom of the tank and soak overnight then empty through the filler neck.. do the same again(1 gallon) only shake the tank viigorously side to side and longways then empty...(best done with two people)...repeat until flushing liquid becomes clear. there is a very good chance that when all the residue is removed the tank will have become porous...specialist tank repairers up and down the country will line it and coat it (at a cost) a new tank from MB is GBP 400 +....secondhand tanks can be suspect.you must use petrol quality hose and fittings but you will probably need to purge the steel pipes along the chassis by pumping heating oil through them with a pump oilcan until the fluid flows clear.. new filters are a must and the accumulator should be changed to ensure the whole system up to the distributor head is clean..to finish the job fuel lines in the engine bay and to the injectors must be purged along with the cold start regulator....you might try running the engine after cleaning the plumbing along the chassis but chances are you will have to do the rest of the system to get the engine running properly... be methodical!! if you miss a section the pump pressure will push the residue into the filter at the fuel distributor head. ***All seven injectors will have to be removed and serviced...
I've already done that.
The fuel pump works, static and active (pressurising and cranking).
Fuel is getting through the distributor to the injectors.
By pouring fuel direct the engine runs (until the fuel is exhausted).
When the fuel pump is continuously running (but by use of a jumper) fuel pressure is evident, but seems to be 'flowing' rather than under heavy pressure.
After continuous operation for a few minutes, cranking the engine produces a 1-2 second attempt at starting and then nothing.
Loss of initial fuel pressure?