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Hi chez,
the fuel pre-pump test worked this morning. then the car kicked over fine, first go.
That's a good sign. But I'm not real sure about the Check Valve theory, because it isn't meant to hold pressure overnight (the test is for 20 minutes). I think it's more apt to be a "delivery" problem.
I'd like to start by testing fuel pressure, but with K-jet it requires a special guage/valve set-up. So the best we can do is go after the "usual suspects" by other means. Here are the things we can test:
1) Fuel Delivery Volume. (You could use some help with this, or a long pair of wires and a switch so you can control the fuse 5 jumper from the engine area). A neater way is to rig a pair of switched wires plugged into FI relay harness terminals 30 and 87/2, with the relay removed. (Even better if you add a 10 amp fuse in the line.)
If Delivery Volume is low, it could be due to low pressure, but we can still test...
2) ...Both pumps for running (pull fuse 5 and put 12v to left contact for Main pump, then right contact for Tank)
3) The current draw for each pump (if your meter can measure at least 10 amps of current), using the meter between 12V and the fuse 5 contacts as above. (Main pump is 9.5 amps maximum. A weak pump will be lower, I believe. The Tank pump, should be 1 to 2 amps.)
4) A short hose in the tank, which connects the "prepump" to the outlet pipe. Over time. this hose rots and leaks, which reduces the output flow to the Main pump (even with a full tank)—and causes the Main to suck air if the tank level is below half.. This is not a fun job, but given your tool kit, I'd say you're up to it. And, given the age of the car, it's quite likely to be needed.
Here's how to test fuel delivery:
A) Loosen the tank filler cap, and disconnect the fuel Return hose, where it conncts to the return pipe. I'm hoping it's in the usual K-jet location, just below the filter on the firewall left side. Have a rag handy to trap any fuel spray as the connection opens.
B) Put the end of the return hose into a 2 liter plastic bottle. Also set your meter to monitor battery voltage during the test period.
C) Start the pumps, and when fuel appears, start measuring for 30 seconds, then stop the pumps. Try to note/mark the fuel level at the 30-second point, as some flow will continue after the pumps stop.
Assuming 12 volts at the battery, the quantity should be 1 Liter.
Lets leave it at that for now. Let me know how it goes.
Bruce
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Bruce Young,
'93 940-NA (current)
'80 GLE V8 (Sold 5/03)
'83 Turbo 245
'76 244 (lasted only 255,000 miles)
73 142 (98K)
'71 144 (track modified--crusher bound)
New 144 from '67 to '78
Used '62 122 from '63 to '67
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