Hello everyone,
Had a question I wanted to run by the experts.
I've had this 745 turbo for about a year now.
Since the time of purchase she's always had a hard start.
When turning the key you really have to hold it in the forward position and let the engine crank for a second or two before it starts. Recently while driving around she acts like she's going to stall but then doesn't? Not sure if that's related but I thought it was interesting.

Now for those who read this forum you know I have done some major work to this car in the last year to keep it on the road. Heater core, full brakes, booster, master cylinder, throttle body cleaned and adjusted to factor settings, intake manifold gasket, exhaust manifold gasket, knock sensor, water temp sensor, Pcv system. Plus cleaning and all fluid changes. The cap, rotor, plugs and wires are from last year sometime before purchase.

Now the hard start seems to be getting worse. The engine is not throwing any codes? What am I missing? Are we talking new starter or is there something that just needs cleaning?
What ever thought you have would be helpful.
Thanks, Greg

 

Bump!

 

Does this happen full tank or half tank? Or all the time? Could your pump be little defekt? There is a valve in the pump that stops the gas from returning back,to keep he pressure and that could be malfunctioning. Happens cold start or warm start? Can also be the radiorelay on the watercooling reservoir.Its a kind of help relay for the fuel injectors

 

Yes good points there.....

The fuel filter and check valve were replaced together recently.

The pump does not seem to give me trouble at slow speed or the highway, no hesitation or *******. Although I have never checked the real working pressure at the rail b/c there is no valve like on the newer models.

The hard start is usually a cold first start or if it sits for a few hours.
Come to think of it after the engine is warm the start is easier, Hmmm?

I keep reading about this water cooler sensor at the water tank, what's that all about?

 

This relay sends a signal to the fuelinjectors to fire.If it does not send this signal then your car will not start.However you should get a code if this fault occurs.So i dont know what to say since you dont get any code.You could open this relay and solder the joints/points if you wish.Or you can buy one from the junkyard cheap.If the start failure is primarily in cold engine then it could be the temp sensor Of the motor that is giving you problems.

 

So now with the car running I'm getting a code.
In the #2 slot the code reads 121.
So that's a Mass air flow code maybe the connection is bad?
I try the unplug it and plug in diagnostic first.

 

OK, so disconnected the MAF and the check engine light came on finally!
The engine seemed to run "better" well actually faster revved up to 1000RPM.
And normally I have the idle set to 750-800. Strange that it would run better with out the MAF connected? That means it's either clogged or actually it's time for a new one! Crap is there anything else that can be done to diagnose the possible problem? I would hate to through $300 dollar parts at this one.

 

Glad to know you got a code.You can try to change with a friends if you have one and see if it helps.Also Try cleaning the connections to and from the sensor with electronic cleaning oil and se what happens.

 

Cleaned contacts and cleared codes.
Back to square one. She still hard starts cold.
The thing that gets me is there's no codes?
If there was a problem shouldnt I be expecting one?
Or maybe I'm thinking with an OBD2 mind.

 

I am not that familiar with the 740 series and definitely have no experience with the turbo model. However, I recall reading in the forums about a technical service bulletin for 90s models 740s that causes hard starts. The TSB was to rewire the cold start injector so it engaged only when the starter cranked. I guess the original wiring was to engage the injector when the key was put in position II. Search the forums here and perhaps you can find some reference to it. Like I said though, I'm not sure the TSB was for the turbo model or not.

Good luck.

 

Thats a good guess thanks.
But this model does not have a cold start injector.

 

the LH2.4 cars don't have a cold start injector.

its LH2.4 if it has the diagnostic reader block on the left strut tower. I believe by 1989, nonturbos were 2.4 and 1990 or 91 was the cutover for turbos ? don't quote me here.

 

Yes I think that's the one Pierce!

 

Did it again yesterday.
Hard start, turned the key and tic, tic, tic, tic, verroom.
But it did not start. Turned the key again and it started.
No codes, should I start checking the injectors, plugs?
Are we back to basics?

 

I always think of cranking without starting as 'ra-ra-ra-ra-ra-ra', not 'tic tic tic verroom'

right after cranking and not starting, pull a plug. is it wet? then your problem is likely spark. if its dry, its probably not getting any fuel.

when you turn the key to the 'on' position (before starting), the fuel pumps should run for about 1 second to build up fuel pressure. if they don't, the fuel pump relay is a prime suspect (but so is the wiring and anything else involved)..

 

Yes, ra-rah is more accurate, that's funny!
Except it almost always starts otherwise I would pull a plug to look.
It only happens once in a blue moon or if I'm late for work.
To see which it is could I give it a turn and stop before it starts?

That's a good tip about the fuel relay. I'll listen for it to turn on.
I wondered if when the heater core quenched it spilled on some of the relays or wire's? I don't really know as it happened before it was mine.
Seemed like most of the coolant followed the air ducts though when I cleaned it all up.

I starting to think it might be a great idea to just replace all the old relays and fuses like what's his name does?

 

on a 740/940, the fuel relay is behind the ashtray. its actually called the main relay or something, and its a double relay, one section powers the fuel injection and most everything else in the engine, and the other section powers the fuel pumps.

this is the wiring diagram for the injection on a non-turbo 92 740. the turbo is almost identical.



2/13 is the fuel pump/injection relay in question.

a dirty trick if you suspect the fuel pump relay is to jumper power to fuse 11... you can get this power from fuse 12 or 13.... this will make the fuel pumps run always-on if the ignition is on. they shut the pumps off when the engine is not running purely as a safety thing (so if the car is in a crash, its not pumping fuel potentially into a fire or whatever).

 

I have a few things that might be useful just for your knowledge:

If yours is a 1990 740 T, then it must be LH 2.4. My old '89 740 T was LH 2.2. And my current 1991 240 is a 2.4. But the main thing is that LH 2.2 does not have any OBD unit. So far as I understand (and confirmed with my experience) if you have an OBD unit, then it must be 2.4 or newer. So, the LH 2.4 info ought to be relevant here.

 

I think thats what I said in post #12

 

So it is. Sorry, read it too quickly.