askulte

AKA Andris is trying to start the *&@^$#. The IC and 9" rear is done, and now I'm trying to start her back up. I'm running DFI (which may or may not be the problem), can't get the laptop to sync with the ECM, and fuel pressure is constant at 30 psi. I'm going to try and connect the fuel pump to a direct 12V and see if that'll bump up the pressure a little. It's not even catching :/ I know one plug wire is fried, but the rest should be OK. Is there some way of checking for spark? The last time I did the screw driver trick to see the spark jump, it fried my Accel coil. Oil pressure comes right up as it cranks over. It's been sitting since I snapped the axle in November. Any ideas?



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Andris Skulte
Skulte Performance Designs
Z28tt-89 IROC T56 DFI Twin Turbo
http://www.skulte.com

Grim Reaper

Andris, hook an old timing light to each spark plug. Those older timing light's intensity often varies with the intensity of the spark. You don't care about the actual timing, just if you are getting a decent spark to each plug. This is where you can hook the old timing light and notice the intensity of the light for each plug.

Just a thought.

askulte

Thanks for the idea. I only had a self-powered light, and it was sparking regularly. I am getting spark, so the DFI must be partially working at least.

That leaves fuel. I plugged a noid light into both banks of injectors, and no flash, so no injector pulsing going on. All fuses (inj1 and inj2 among them) are good. The fuel pressure does not pulsate and sits at 30 psi, and I do not hear the pump either... I'm going to try to hook up the 12V to the pump to see if that helps any, and I will check the DFI harness for injector driver pins with a DVM.

A.

maniacc

Andris,

Another quick and easy way to test for spark is, take the spark plug out of the hole and stick it back in the wire and ground it out against something with a good ground.

later
larry

askulte

Update - I'm an idiot. I had plugged the ECM into the original GM ECM plugs, not the DFI plugs. The GM plugs have now been covered in electrical tape.

However - she still doesn't start. I'm getting fuel now (the noid light flashes) and you can smell the fuel (and the pump runs). I even tried clear start mode, to no avail. Can old gas make it impossible to start? The DFI still won't link with the laptop.

Andris "Did you know you still get spark without an ECM connected?" Skulte

89ProchargedROC

ignition control module

car will crank but wont start if bad. If it is bad the sensor on the distributor wont tell the computer to ground out the injectors and wont fire.

also, are the wires hooked up right? you know the plug wires?

Grim Reaper

I left my car for almost a year (I was sent out of the country on a prolonged business trip) and had a dickens of a time getting my car started.

The old gas causes the injectors to "gum up" with "varnish". I had to run a couple of tanks of fuel injector cleaner to get them to work right.

Sorry I can't be more help with the DFI. My expertise is more specialized to the SD ecm/eprom.

askulte

The injectors are firing (see above). This car does some weird things sometimes. After a severe stall (like letting the clutch out way to fast, or spinning the car) it does not like to start. She'll crank forever, but will not catch. The only way to get it going at that point is to bump start it. I'm going to try spraying some ether into the plenum to see if that helps.

Andris, crossing my fingers

Grim Reaper

Andris, my post on "varnished injectors" relates more to what happens "inside". From a test light, they would still look like they are working.

As for the "hot starting", your DFI may need some tweaking in this area. With my SD ecm, there are 3 distinct start up modes": cold, warm and hot. These are controlled primarily the MAT and CTS temperatures to determine which mode to start with.

Generally, cold start gives you the most fuel (starts off at 12:1 and then slowly leans itself out as it warms up). While warm and hot start leaner (hot very lean).

It sounds to me like a fuel delivery issue. It could be your DFI is setup right, but there is insufficient fuel pressure or fuel being delivered at the injector such that it won't overcome the "warm or hot" start part of the DFI code.

And easy way to test this would be to install either a resistor or potentiometer so that the MAT and CTS read quite low, and see if it will start when hot. Then you know that it something within DFI (other than weak fuel delivery outright).

askulte

AFAIK, the cold and hot start tables and start up enrichment are correct. The IAT and CTS are around 40 degrees, and I'm using the same DFI starting calibaration files I've used for a few year now with success. Fuel pressure is at 60 psi with 0 vac (gotta work those 30# injectors!), with the minimum idle pulsewidth at 1.7ms. I'm running out to get a can of starter fluid and 8 new plugs, and will be sure to let y'all know if it works Thanks for the help.

A.

askulte

No spark now :/

A.

DARCOM

I thank you fried your DFI box if you cant
get a readingfrom a labtop.
also if your dfi is pluged in right you should
hear your fuel pump come on for a sec.
the wiring for your dfi is
diffrant than your stock cpu.
and its easy to fry if it gets 12 volts to
the wrong pins.

check out my simple page at:
http://darcom.home.texas.net/

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388 superram, dfi, vortech r trim ,n.o.s.,alki injection,
dart iron egael heads,50 pound injectors, heaman full headers
duel 3' ehoust,and flowmasters, ford nine inch with 370's
ronal rims with nitto drad raidals.

askulte

Laptop connected fine (had to boot into dos, rather than exit to it). Now no spark - it sparks with the 4 connector plug removed from the dist, which means the pickup coil is bad. Sure enough - it's toast. I snapped a little magnetic prong off as I was removing the coil shield, so it's time for an MSD distributor. Thanks for playing

A.

askulte

More fun and follies I drove 45 miles to Kevin Crain's place and grabbed his spare distributor which was running great when he removed it, and in perfect condition. We popped in Kevin's distributor, connected all the stock ignition hardware (unplugged the Accel 300+ box) and connected a known good coil. Still no spark. The troubleshooting begins with the service manual, and when we unplug the 4 connector plug on the distributor (ignition module) we get spark and she catches.

This no places the blame on:
1. A bad ignition module in the distributor (voted no, since we put in a known good one)
2. Bad wiring (again no, we checked all four wires and they seemed continuous)
3. Bad ECM.

Long rambling:
There is a procedure in the service manual that tells you to test the timing bypass circuit (Tan/blk, pin D5 on the GM 1989 MAF harness amd Pin B2 on the DFI) with a "test light to battery voltage". What kind of test light is this?

This probing should switch the ignition module EST circuit (White, Pin D4 / B1 as before). "As the test light voltage touches circuit 424 (timing by-pass pin on the ECM harness) the module should switch" (from previous <1000 ohms to 2000+ ohms) You should see the ohmetter still connected to the EST pin on the ECM harness plug over-range past 1000-2000 ohms. "The important thing is that the module switched". In otherwords, it tells you the module is good if it switched and the blame is the ECM.