Pettinger1

I bought a running 1980 928 for my son and I to work on about 8 months ago. Typical project car with door panels and electric wiring guts laying all over the interior, but the engine and drivetrain were running STRONG!

The fuel tank was leaking from a crack, so we replaced it with a salvaged 1979 Euro tank, and it was still working OK.

After sitting for a couple of months, it will now only catch and run for a few seconds before dying off. The only idiot light we have lit is the oxygen sensor, but pretty sure that all the lights on the dash probably don't work anyway, so this may be misleading.

Here's what we've done so far, and what we know:
1. New fuel pump and filter
2. Cleaned gas tank
3. Removed all injectors, hooked them up to a power supply and blasted them clean with compressed air (all are clear, but probably not perfect).
4. Removed test nut from passenger-side injector rail to confirm we're getting pressure to injectors, but haven't hooked up a pressure gauge yet.
5. Ensured that the vacuum hoses from fuel distributor all the way to the firewall side of the injector rails are in place.
6. Replaced fuel in tank.
7. Re-charged the battery. Couldn't handle the repeat tests starts.
8. Successfully run the engine with starter fluid sprayed into the air intake, albeit touch and go with revving the engine with subsequent stalling.

It seems to me we have a fuel supply problem, but are completely stumped about what to do next!

If we do attach a pressure gauge to the starboard injector rail, what should the pressure be?

Any other brilliant insights???

michaelathome

Pettinger,

The fuel rail pressure on a later S$ should be above 40psi IIRC, maybe close to 45psi. I would have to go back to the manual. The leak down after pressurizing the rail should take several hours.

My guess is that it could be any of the following:
- Rail pressure
- Injector flow
- Regulator pressures
- Vacume pressures to the regulators.

Not an easy list to overcome but very do-able,

my 0.02

Michael


P.S. congrats on your purchase and hope you and your sone have a great time with the rebuild.

Pettinger1

Can you school me on Regulator Pressures and Vacuum Pressures to the Regulators?

I'm good with rigging up a temporary pressure gauge to the rail, but all my other diagnostic capabilities are completely plumbed at this point.

James Bailey

It is starting on the cold start injector, the 9 th injector. Your fuel injection is NOT injecting the 8 injectors are not getting told to inject. To check get a noide light cheap at most autoparts stores and see if it blinks when cranking. Possibly the injection relay is not working , or the injector ground is missing...

michaelathome

Pettinger,

Do you have a copy of the work shop manuals? Do a search and you should be able to find the values/manuals.

I do not have a set handy as I am working off of my laptop and my PC has the files.

Michael

soontobered84

I don't believe that any 928 L-Jet system is pressured that high.
CIS cars use much higher fuel pressures.

I would think James is on the right path: Relay, Relay, Relay.

Pettinger1

Jumped the relay and also plugged in an additional spare. Same problem. Fuel pump CLEARLY working fine (1-2 second buzz when relay in place, constant <<on>> when relay jumped).

Don't have a shop manual copy, but not sure they would help. Clearly a male problem with reading the directions first...

Noid light? Did a quick search and will get one tomorrow.

Any more specific suggestions on troubleshooting the injector ground? Obvious enough to replace injector relay...

And, will rig up a pressure gauge to the rail. Not sure how to differentiate between a CIS and L-Jet system though...see pix of the fuel distribution box at the front of the engine. Can anyone tell me if I have a CIS or L Jet from this pix?

Guy

L-jet

Pettinger1

Thanks! Will look for ~40psi.

Any suggestions on diagnosing the injector ground problem?

Guy

I believe the injector ground is located on the passenger side cam cover about mid way but I haven't worked on my 81 is some time so I am a little rusty.

The Forgotten On

Both injection grounds are located on the bolts that hold the metal pipe with the air valve on the end that connects the smog pump to the cat on to the cam housing. They suck to get to.

soontobered84

[QUOTE=Pettinger1;11020848]Jumped the relay and also plugged in an additional spare. Same problem. Fuel pump CLEARLY working fine (1-2 second buzz when relay in place, constant <<on>> when relay jumped).
QUOTE]

To replace the injector relay with a jumper requires 3 terminals to be jumpered together. If you only jumper 2, it won't work. Did you jumper 3 terminals? IIRC terminals 30 to 87 and 87A

Fuel pump jumper is just terminal 30 to 87.

michaelathome

Corrected my earlier post. 40-45 is about right.

Michael, too much

danglerb

Isn't it about now somebody says "green wire"?

A green wire from the distributor to the 14 pin connector on passenger fender and fuel injection brains, carries the spark info/engine rotation etc.. Connection head shells tend to fail.

Pettinger1

Forenote: the car's been running for about a month and a half now (since the last weekend of January).
If I understand what my father did, he replaced the relay and the green wire, and after replacing the relay the car ran. Green wire was already shipped, so we replaced the corroded one with the new one. Car was still running rough, so we replaced one of the...sparkplug? wires, which seemed to fix the problem. Of course, now we have new and different ones, but they don't seem to be too serious (starter motor has been finicky) and I'm planning on replacing it in the next few weeks (whenever I go back to Jacksonville).