I'm finally getting around to working on my brother's '79 242 with CIS injection. It sat for several months with a bad fuel pump so I replaced the pump with a good used one. Car would then start and immediately die unless I spray starting fluid into the intake in which case it runs until that runs out. I thought the fuel filter may be clogged since it was very old so I replaced that tonight, however I'm still seeing the same symptom. If I disconnect the fuel return line and manually engage the pump I can hear the pump load down as pressure builds up in the line, however no fuel ever comes out the return. I also noticed that with the pump running I can't lift the airflow sensor plate, I didn't force it but it certainly doesn't move freely as it does with the pump off. Anyone got ideas? I'm starting to wonder if the fuel distributor has somehow got mucked up.
In article , snipped-for-privacy@hotmail.com says...
Ideas in no particular order.
Blow through the return line to make sure it is clean all the way to the tank. The metal lines can be damaged if someone just jams a jack under the center of the car and tries to lift it NASCAR style.
The 4cyl motors use an upflow fuel distributor, the 6cyl use a downflow. So lifting up the plate should make the injectors spray on a 4cyl, pushing down makes the injectors spray on a 6cyl.
I think that '79 was the first year of the "small" airflow sensor plate. If so, the line pressure regulator and control pressure regulator check valve share the same horizontal bore in the fuel distributor. In additon to the spring and shims on the needle valve there is a small o-ring that can leak and make the car very hard to start. It can stick but not very solidly. If it has a frequency valve then when the valve is in the default shut position there will be no flow. It may not be running when you jumper the fuel pump relay and there would be no flow on the return side of the circuit. If you can break the line loose at the fuel distributor however there should be fuel present but very little pressure. Pull out an injector so you can see what is happening. Jump the fuel pump relay so that the pump is running. Pull the intake bellows out of the way and grab the 10mm headed screw in the middle of the air flow sensor plate and lift. The injector should spray. If it doesn't try rapping on the center of the fuel distributor to see is the plunger comes unstuck. If not delete all the above steps then pull the fuel distributor off. Be sure to keep track of all the little copper seals. You will need them again. Ideally they should be replaced but we're testing here. Keep track of all the plastic screens/valves in the vertical outlet ports and the rubber o-ring between the fuel distributor and the airflow housing. Carefully pull the plunger out of the bore in the center. Note the orientaton of the plunger as you remove it. Clean it and the bore with carburetor cleaner to remove any varnish that is keeping the plunger from moving. If it is rusted or blistered it is finished and you'll need a different fuel distributor.
Make sure the arm for the airflow sensor plate moves freely in the bore. If it needs to be recentered you can put three 0.002" feeler gauges around the edge of the plate and then loosen and retighten the center screw.
Another possibility is that creatures have shredded the air filter and built a nest in the air box that got sucked into the bellows tube and may be interfering with the operation of the counter weight on the air flow sensor plate arm.
I disconnected the return line under the hood right near the fuel filter on the firewall so there's nothing but a rubber hose between the fuel distributor and that fitting. I verified the presence of fuel at the filter by turning the pump on with that disconnected and got a healthy looking flow. Should fuel come out the return line if I start the pump without the engine running? I would think so, but I've never tried that on a working car.
I forgot to mention, the car does not have the original motor. This is a Canadian B23E of unknown year that I installed which is complete with the whole fuel system it came with. No frequency valve is present on this particular setup though I've thought about installing the old B21F injection system to hook up the lambda sond system.
Thanks, I'll try this the next time I go out there and see what happens.
It moves freely with the pump off, but sticks down with the pump running. I haven't pulled very hard to see if it frees up though, I didn't want to damage the delicate mechanism.
I'm pretty sure this isn't the problem, as the flow plate feels fine with the pump off, and it will run if I spray WD-40 into the airbox.
Well the gas is certainly past it's prime, however symptoms point towards something else, I'm just not sure entirely what. Thanks for the suggestions though.
The only things in the circuit that restrict return flow are the control pressure regulator and the line pressure regulator. IIRC the line pressure regulator puts about 5 bar+/- to the top of the fuel distributor where it flows around the plunger to the bottom side of the fuel distributor where it is regulated according to the temperature of the bimetal strip inside to a pressure rising from 1.4bar to 3.7bar and then whatever volume is left over with the injectors closed is bypassed to the return line at very little pressure. So the answer would be yes. Since the plunger is a spool valve the amount of return flow would depend on the position of the plunger. Tap on the top of the fuel distributor and see if it breaks loose.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.