newworld

87s4 aut.

continue to have a hard start cold, need carb spray in the intake and starts right up. after first start of the day, subsequent starts are normal.

new temp sensor, and it ohm perfect, also spliced new wires to the sensor plug and new sensor plug female.

new regulators, dampers, no fuel from vacuum hose etc.

new fuel filter.

at this point, fuel check valve, but curious if there were any other troubleshooting before i continue to change things.

drwhosc

I have the same issue in my 88 S4. trouble shot everything , but found it to be a leaky injector. Still do not know which one, but you can check by hooking up a fuel pressure gauge, it should hold pressure after you shut down. I do think you need to have a functional fuel check valve on the pump, so this will not point to a leaky injector. I replaces just about all my components, and this is what I have left. Will be curious to see what you find.

AO

Are you running stock chips?

It sounds like a cold start issue. The Temp II sensor (the one on the passenger side of the water bridge) tells the LH to add fuel as your starting it. There's also a cranking map that add even more fuel.

How's the fuel pressure?

The only other thing I can think of is that the injectors might be a but plugged up. You can try some BG44 or Techron in the gas and see if that cleans things up. If i think of anything else, I'll post it.

AO

Oh yeah... In my signature, click on the "Official LH/EZK Test Thread! Quick reference from WSM for Testing." Read that.

newworld

87s4 aut.

i did put a lot of chevron techron in there, no change.

i put a noid light on some injectors and they fire correctly.

interesting, if you jumper fuel pump, i can hear fuel pump running, but still no start.

it only starts cold start with help from carb cleaner in intake.

im scratching my head on this one. there are no lh, ezk issues, good spark etc.

John Speake

Did you ohm out the temp 2 sensor at pins 13 and 5 of the LH ECU ?

newworld

i ohmed the temp sensor, on read from a chart on ambient temp,

then i thought wiring was a bit frayed near plug, so i replaced and soldered and new plug.

i thought for sure that would cure it. i had to wait overnight for the test, and then again no first start without "help"....

i have not ohmed lh plug, i will do tonight, i will measure 13 and 5 pins....

drwhosc

check your fuel pressure at the front port. It should hold its pressure for quite some time after you turn off the engine. If not, you have a leaky injector or a bad check valve. I think this is going to be your problem.

AO

It's not a leaky injector. He's having difficulty getting it to start and is adding fuel to "jumpstart" it. A leaky injector might cause flooding which would also cause hard starting, but adding fuel would not solve this. Furthermore, a leaky injector would not present itself ONLY on cold starts.

I think John is on the right path in suggesting ohm-ing the temp II at the LH.

If that checks, I'll stand by my fuel pressure hypothesis.

SteveG

I had a similar prob on an '85, incl use of start fluid. Temp II and LH checked out. I cleaned all grounds and coil wire connections (and coil grounds) and problem went away.

AO

Good point. The Temp II needs to have a good reference to ground. You should try ohming between the body of the temp sensor and the cross brace to see how much resistance is there. I had a waterbridge that had been powdercoated that would no long ground well and hence the temp II sensor has issues providing a good signal to the LH.

newworld

update.....87s4 crank no start without help.

i have a new temp sensor installed and even got a new plug as well. that did not solve anything.

then i found in the wire, some spliced buts, and some wires were loose, i soddered it, and thought i solved it. no joy.

then finally after 2 weeks away from the car, i tore apart the insulation wrap on the wires, and found another butt splice loose, i soddered again and voila, it started everytime.

then i drove it around for awhile till it got hot, and then shut off engine.

again no start!!!

i squirted carb cleaner in intake and starts up again.

so right now, i think i know it is the temp sensor wiring, but i soddered it real well, could heat affect the wire itself?

i wrapped it in loom, so i am wondering what my next move is.

i thought i had solved this one.

i am going to wait till car cools down and try a no help start and see if it fires.

newworld

87s4 aut...

as far as whats new, new temp sensor, all new relays, fuel pump fires, starter cranks, good spark, fuel injectors fire with noid test, maf was checked and good, seems like it doesnt get enough gas?

all new fuel regulators and dampers and lines.

newworld

87s4 aut.

waited till the car cooled down, and it started right up.

cut engine off and started again no problem.

so thus far, if the car has been running and hot up to temp rad hose upper= 197 deg F, then you shut off engine. hard to start, cranks but doesnt start.

if add carb cleaner, starts right up even when hot.

if car has sat for awhile, then it starts without carb cleaner.

newworld

87s4 aut.

question....if hot start is a problem, and cold starts are now fine with wiring to temp sensor and temp sensor working.....

is there a way to make every start a "cold start"?

it seems that there no fuel during a hot start. if i use carb cleaner in intake it fires right up on hot start, so injectors are not leaking etc.

if there was a way to make the car think that it was a cold start even when hot, i think it will start every time.

clearly my fuel pressure is dropping after hot shutdown. i have new regulators, new dampers etc.

anyone know how to mimic a cold start in the wiring let me know....