Thread: 93 Hard Dash, Spark Plugs and Fuses

Two steps forward, one step back.

To celebrate getting it running properly I took it for a drive in the hills, found a very soft muddy patch and got it completely covered in mud.
So much that I had to waterblast it outside and underside when I got home. That took a week for the distributor and EAS to behave as normal.

After getting into the dash I now have 3/4 of the heater backlights working. The cigarette lighter sockets too.
Some previously unhelpful sod took the 6 fuse holder under the front passengers seat and remounted it in a completely inaccessible place. I had to pull up the carpets, undo the seat side cover and the seat base cover to unscrew it and get the lid off.

So blown fuse found and lighter sockets are now working.

Then today I went looking for the idle problem and found it.
Tamper seals missing on the base idle screw and no-sealant between the halves of the plenum.
Probably the same previously unhelpful sod had tried to compensate for a stuck open thermostat and/or plenum air leaks by cranking on the base idle. When I replaced the thermostat it would idle on the stepper motor and keep conking out.

With the plenum sealed up the idle was then almost stable, but still slow. Blocking the stepper air feed I found that one turn on the base idle screw bought me back to a solid idle.
I gave the stepper motor seats a clean, the shaft some oil and called it good.

But one question. What's with the 5.5mm allen key needed (socket head cap screws) to get the stepper motor block off the back of the plenum?

It's still not perfect, but it's a damn sight better than it's likely been for years.

Okay, here is Mondays diagnostics.

Work done to date (in no particular order).
New thermostat.
New distributor cap.
New rotor.
New leads.
New fuel filter.
Idle stepper motor cleaned, blocked off while idle was reset and then unblocked.
Throttle Position Sensor checked, 0.22v open, 4.85v closed.

Test runs with MAF disconnected and connected. No real difference.
Temp sensor shows 480 ohms when not quite warm which is a bit over 60 degrees according to the info on this page: Fuel injection

Problem:
It still stumbles and misfires starting about 2,900rpm. By 3,500rpm it's just awful.

I did have it running well just after the fuel filter change and before the water-blasting. Chances of enough crap coming through to block up a second filter?

Where to next? Rail pressure?

Try a new fuel pump. Bosch BFP772 kit to suit VN-VR Commodore.

Insert an ammeter inline to your pump. New pump should draw 6A, worn pump will draw 10A+. Anything that blocks a fuel filter has been through the pump and it is supposed to be a precision device!

Todays effort.

Fuel temp sensor removed from the rail and a pressure gauge fitted.
First worrying sign, no fuel came out when I removed the sensor.
Second worrying sign, no pressure registers with key on or engine running.

Fuel pump is using 5A.

So, I'm thinking the relief valve now.

Relief valve is out and holding to 37psi with a bike pump and pressure gauge.

So now it's into the in-tank pump.

Originally Posted by Dougal

Todays effort.

Fuel temp sensor removed from the rail and a pressure gauge fitted.
First worrying sign, no fuel came out when I removed the sensor.
Second worrying sign, no pressure registers with key on or engine running.

Fuel pump is using 5A.

So, I'm thinking the relief valve now.

Using pliers, squeeze the return line to the tank from the FPR and observe the pressure rise. Busted FPRs aren't uncommon. You could buy a ricer boys adjustable reg with gauge off ebay and fit that instead.

Originally Posted by bee utey

Using pliers, squeeze the return line to the tank from the FPR and observe the pressure rise. Busted FPRs aren't uncommon. You could buy a ricer boys adjustable reg with gauge off ebay and fit that instead.

I did it the hard way, took it off (the hardest to reach bolts in the engine bay possibly) and slowly pressurised it with a hand pump and pressure guage. Same way I do turbo wastegates.
It did what it should.

Fuel pump checks out fine, enough pressure to wind my 35psi guage off the dial and then blow the hose off.
Cleaned some rubbish out of the bucket and a loose earth fixed which should sort the fuel gauge out.

Back to looking at the lines and filter it seems.

Measured the fuel pressure, first at the pump (solid 37psi) then at the rail (32psi raising to almost 40psi when revved).

While doing this, I noticed it began to idle worse and worse as the battery dropped.
So I put a charger on it. And with the charger hooked up, it's not misfiring.