Hi Brickboard folks

My daughter's 1988 740 (130k) would not restart after driving any distance and soetimes would stall while driving and not restart.

I started the 740 ran for a few seconds then shut it off. It started right up. I shut it off a second time and it started right up. However, the third time I shut it off, it would just crank and crank (like it was flooded when the engine shut off - perhaps the injectors were leaking?)

I waited 15 minutes and it would start right up again. The third time it would not restart again.

I pulled the vacuum line off of the fuel pressure regulator and gas squirts out of the vacuum side so I needed a new regulator.

I put a good used rail on to the 740 and it will not start at all.

I put the original rail back on after changing the regulator and it still won't start.

I had pulled off a crankcase oil screen to clean it and I plugged the big hole in the intake hose. I also plugged a small vacuum line that teed from the oil screen.

I get 12 V at the both injector pins and the tach bounces when I crank the engine. I put in new plugs, cap, rotor, wires and a used ebay distributor.

Please help

when you crank the motor, the ecu pulses the gray wire to ground at the injector so the injector can fire. check that wire through all the connectors back to the ecu. all that tugging on a crumbling harness might be the poroblem. good luck, chuck.

Can I run a jumper from the ECU to the rail? I will try the scope now that I am near AC. Can I put a needle valve downstream of the regulator with a gage between the regulator and the needle valve to try and set rail pressure? Is rail pressure 60 psig on a 1988 740 NON turbo? Do you know anyone that wants to sell a fuel pressure test gage with adapters?

Thanks for your support

the jumper will work, if the ecu is. the fuel pressure is taken at the rail inlet and should be 42psi/no vacuum, 36psi with. where did 60 come from? don't know about putting a needle valve someplace, or of someone selling a gauge kit. probably, by the time you spend the money on a tester, you could've had someone test it.

here's a thought-go to the outlet of the fuel pump under the car. get the simplest pressure tester you can and tee into the outlet line. make sure the gauge goes to 50psi or so, no lower. you might also see a schrader valve under there and ford has used those for a while. might be an easy kit to get. i've seen valves on volvos but i can't tell you when they started using them. good luck, chuck.

I put the oscope channel one probe on the gray wire on injector #1 and clipped the oscope cable shield wire to battery ground.

When I put the ignition to ON, I get the dorsal pattern you described. When I crank it, I see a spike on the bigger of the 2 dorsals. It sounded like it wanted to start this morning but did not.

It seems that the pulse is there even when one turns on the ignition switch. I suppose that the engine does not flood because the pump is not running until one cranks it?

I will hot wire the pump and see if it fires off.

Any other sugestions?

i can't think of any good reason for the injector to pulse until the car cranks, unless the dist pick-up is in just the right position. the fuel ecu needs the signal from the spinning dist to command injection. the fuel pump and the injectors get power from the same terminal on the fuel pump relay. scope the power side of the injector while cranking, too. should be a steady 12v. the double dorsal doesn't sound right, nor does the spike on 1 of them. again, the double pattern may be a cold start strategy i've not seen before. any chance you can post the scope pattern? if it's digital, maybe it'll store and recall. is the harness and the connnector at the dist ok? what about the rest of the engine harnesses? good luck, chuck.

I jumpered the main fuel pump (pink wire) and the engine tried to catch then quickly died. Repeats - quickly dies.
I ordered a fuel pressure regulator and pump relay along with a new flame trap. i will sketch the oscope pattern in word but how can I attach the sketch?

if the car starts and stalls with the relay jumped, the new relay shouldn't help. while you were doing this, were you looking at both wires on the injectors?

i don't know how you can ship the drawing, sorry.

I am going to put the new regulator on tomorrow. I may not be able to get to a computer next week but will report back on 08March with results

Thanks for being there

I will try your suggestion this weekend and report back on Monday. When you say "scope the power side of the injector while cranking", do you mean the green wire on the injector?

Thanks for sharing your expertise