pirrello

I own a 1993 Del Sol S - Intermittent no start. The F1 relay sequence, when working, I can hear the series of clicks then the fuel pump pressure up then it starts. Otherwise nothing - Tested F1 relay and it is good. Voltage at interior relay fuse block (18 - 7.5 amp fuse) is zero. Tested continuity on the F1 harness, ignition switch harness and fuse block and all good. Voltage at the distributor has zero on the BLU/WHT wire which seems to run everywhere. Jumpered the F1 harness to verify fuel pump operation. I think it points to the ECM or igniter. Can anyone tell me where the BLU/WHT wire gets it voltage or ground from (beside the battery/chassis) or should I start all over???

Former User

Fuse 18 only gets voltage with key in ON(III).

Have you already resoldered the main relay and cleaned and tightened the G101 ground on the thermostat housing?

pirrello

Thank you. Main relay re-soldered, no change, replaced with new main relay, no change, ground cleaned and re-seated, no change. Can we start at the beginning? Let's assume I have not sequentially diagnosed this problem in the proper order. The condition is - crank, spark, and no fuel pressure. Condition is intermittent with 1 out of 100 key turns results in main relay clicks and audible fuel pump operation and pressure up and run. Jumpered main relay plug and have fuel pump operation.

Former User

It's most likely a bad ECU.

Do this test:

Turn key OFF.

Unplug ECU connector A.

Use a spare wire to ground the Grn/Yel wire at pin A7 in ECU connector A to the metal frame under the dash.

Cycle the key from OFF to ON(II) multiple times. Does the fuel pump always run with the key in the ON(II) position?

If so, the ECU is likely bad. Remove ECU from car and then remove the covers. Do you see any blown/burnt or leaking capacitors?

Former User

What you're calling A10 is almost surely A7 or A8. Verify here:

.:FFS TechNet : OBD1 ECU Pin out Schematics :.

pirrello

We have a winner - I counted the pins wrong and you are correct sir. A7 shorted to ground
runs the pump when cycling the the key to ON II. ECU???

Former User

Most likely.

pirrello

$250.00 for the part is okay if "most likely" pans out. Are there other diagnostics I should preform to move "most likely" to "absolutely"? I am subscribing to your mantra "Don't guess. Troubleshoot."

Also, I have PCB level experience. Do you have a link to the ECM circuit design or is it a waste of time?

Former User

Do you need a P06 ECU? That should not cost $250. Check the Marketplace and eBay for prices. Be sure the ECU matches your transmission.

You can remove the cover and look for blown or leaking capacitors, though not finding a damaged component by visual inspection does not rule out a bad ECU.

There are a few more tests that can be done, but a bad ECU seems likely.

pirrello

Well a new ECM (remaned) fixed the problem. I could not find any diagnostics making it as simple as the recommended test of grounding A7 - wow - You nailed it again.

Thank you!

Former User

Glad you're back on the road.