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Old 02-06-2019, 09:33 PM   #1
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Join Date: Jan 2016
Location: ON, Canada
Exclamation 1989 740 won't start!

Hey peeps,
so I'm a relatively new owner of my 89' 740 sedan. A little background to the car, it's got a +t swap done to it by the previous owner. It runs lh2.4, and pretty much uses all factory bits and pieces. Right now theres an old leaky t3 garrett Turbo off of an 242gt I believe and uses slimmer red top injectors(#0280155759).
I've been driving it around for the first month or so with no problems regarding starting it up, only that it runs a little rich. I've been having problems with the turbo leaking abit of oil so one weekend I took it off to inspect/clean it, that night I also changed out my coolant temp sensor and swapped the fuel pump relay as a precautionary measure. Once everything was back together I go to start it and nothing. I was able to start it up with some starting fluid and 30 minutes worth of attempts. Once it starts it'll bog down and die if I add any throttle but when leaving it idle until operating temp, I can drive it around no problem.
I then went ahead to change out the main fuel pump and filter, and also the in tank pump/sender assembly since mine was all rusty/leaky.
Still no luck.
When I turn the key to the final position before cranking I do hear the pumps priming. But they don't prime every time, let's say I try to prime them every 3 seconds, 2/5 times it wont, so I'm not sure if it's reached its desired pressure or regardless it should always prime even with the short intervals.
I've also changed the radio suppression relay to rule that out, and checked whether there was a leaky fuel pressure regulator.
I still have some diagnosing to do but have had limited time lately, figured I'd post up and see if anyone's had a similar experience. (I've done some browsing through forums too).

Anyway, if you've read all of this thanks, hope to get this car back on the road asap. I'm probably forgetting some details so I'll do my best to answer any questions.
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Old 02-07-2019, 01:32 PM   #2
Jesse B
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Maybe put the old temp sensor back in and see if it starts? Maybe the new one is defective?
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Old 02-07-2019, 07:32 PM   #3
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Location: ON, Canada

Yea I'm considering retracing my steps there, but looking into it, it doesn't seem like the coolant temp sensor has any input on initial start up.
Although when I was ordering parts I noticed there was an n/a and turbocharged version. Not sure what the difference would be, but the only thing potentially wrong is I got a turbo sensor for an originally n/a block? Doesn't seem like it would cause any issues
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Old 02-07-2019, 08:33 PM   #4
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Just because it's new doesn't mean it's any good...buy a d.v.m. And start trouble shooting, of course the temp sensor has a input when it's cold..do you think it only works at 70°¿ Does it have any codes? Did you check the grounds? Is there vacuum leak? If it ran fine before it's more likely you overlooked something when you put it together....now my 240 became unbearable do drive when it went into closed loop and out ended being the 02 sensor
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Old 02-07-2019, 08:38 PM   #5
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Location: S NJ, a suburb of Phila.

I recently had a brand new coolant temp sensor from a supposedly reputable volvo parts supplier Uro that was totally out of spec and I had to get a good used one. So for sure get a meter and test things.
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Old 02-08-2019, 02:20 AM   #6
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Location: ON, Canada

Ya good point, I do have a meter, I'll definitely start trouble shooting, the free time I had I've spent on changing the pumps and such since I was planning on servicing them anyway.
But can a coolant temp sensor cause a no start situation? I initially changed it incase that was the reason I was running rich. I'll be sure to search the desired ohm readings. My old one didn't have continuity
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Old 02-08-2019, 02:44 PM   #7
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Too long. Didn't read. Click my sig.
No Start Thread
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Old 02-08-2019, 03:21 PM   #8
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Location: Fort Wayne, Indiana

It sounds like we're pretty sure it's fuel system trouble, but I just want to throw in that dying when throttling could be distributor or spark plug related, if it's been parked in rain/snow/moist envrionments.

My 244 (RIP) would do that after going through car washes occasionally until I replaced the distributor rotor and cap.

Could be it has that and other problems, too.
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