s13 sr20 hot, will crank, no start, easy cold start.

[Mountain_Man]

Problem: If I leave the car over night, it starts no problem, first try. The second i get to work, it will crank and crank and crank but no start. i have fuel and spark. ive sprayed brake clean in the throttle body, nothing. ive pulled the spark plugs out, they all spark.

Car: 1989 240sx Coupe, i bought the car last fourth of july from someone i work with at the local nissan dealership. she blew the head gasket on the stock motor and it sat for about 5 years before i bought it. all original, all stock, automatic, sohc, rust free. ive been driving it for about a week with this problem and right now im driving without a cluster. im putting the rest of the interior back together tomorrow.

Engine: S13 SR20 Black top:
-272 BC cams
-greddy front mount
-mushroom head
-metal intake pipe
-ichiba exhaust mani
-isis turbo lines
-arp head studs
-waboro 255 fuel pump
-three inch strait pipe exhaust
everything else is stock. i bought the engine in last november and ran into problem after problem. long story short this car has just been problems. the guy i bought it from a kid who never got his car registered and only put a few miles on the motor over the course of a year. the engine harness isnt in the best of shape but i have all the necessities hooked up. i know i have to be missing something.

I really need help with this car. ive done my research but i still cant figure it out. i know i have to be missing something and any help would be appreciated. this is my only means of transportation right now. i have a rb20 91 hatch but the motor is missing a few piston rings and probably wont last very long. the rb has been my most reliable means of transportation to work and class for almost 5 years but its done.

[Sileighty_85]

Sounds like a bad CTS (Coolant temp senosr)

I hope the ECU is tuned for those cams, If not thats gonna fuck with it running as well

also might wanna change the plug out since they are probably fouled out by now

[R@ddy]

Damn I'm having the same problem. Exactly the same. And its not the coolant temperature sensor

[Sileighty_85]

Check ECU for code

[R@ddy]

No codes man. Sorry don't mean to thread jack, just trying to help both of us haha (me and OP)

[Mountain_Man]

^^^no worries we are all trying to find a solution.

first thing i researched said to check the coolant temp sensor and so i hooked it up, nothing. i couldnt find the wiring for it to back probe it to make sure it was working right. but i am changing the plugs today.

i dont know much about the ecu except that its for a red top. the cams are not tune for the ecu but what would that have anything to do with starting?

BTW Oki represent!!!

[Sileighty_85]

so when you say you "hooked it up" does that mean you replaced it or just plugged it in?

the symptoms of no hot start and easy cold start are classic indications of a bad CTS, it is possible for the sensor to be out of spec but not throwing a code.

Those cams are very aggressive and id be surprised if that engine ran at all if it wasnt tuned for it. cuz those cams will allow more air to enter the cylinder than the ECU is tuned for.

[Mountain_Man]

when i researched the problem, people on other forums were saying it was the CTS, so i looked through the harness and found the plug and plugged it in. i didnt replace the sensor. but im not 100% on the plug because i do not have the best harness in the world and i might not be getting a good signal. i cant find any info on the sensor itself to back probe it and double check. im going back through the harness today to see if i can chase any other possible problem down.

[Sileighty_85]

just find a pinout of the ECU plug and just do an ohms test.

It might be fine cuz that part of the harness should not be altered.

You can get a new CTS from Autozone for 20 bucks for a 1993 Sentra SE-R with the SR20DE.

[Mountain_Man]

put a new CTS in but still same problem. idles a little better but the same problem. i did notice the tps sensor wiring is a little weird. its looks like im going to have to get another harness. the more i probe around in the wiring, i notice more problems. anyone know where i can get a decent price on a harness?

[Sileighty_85]

WS Pre-Made S13 SR20DET Into S13 240sx Engine Harness

[popcorn]

check your knock sensor.

[R@ddy]

i highly doubt a knock sensor will keep a car from starting when it hot. im thinking maybe the harness is messed up, NOT reading the coolant temp sensor. that OR is running reallyreally rich like mine. just waiting on my gauge so that i can adjust my FPR

[popcorn]

that excactlly what i thought. its happened in two cases sr and ka. it does excactlly what your is doing. stars fine when its cold. warm up dont start. you pull the spark plug and they are full of fuel. .

[KiLLeR2001]

new harness + proper tune will most likely solve this problem.

[Mountain_Man]

i checked the fault code on the ecu and it flashed a 34-knock sensor and the tps is wired wrong. i just need to get a new harness and a good tune like killer was saying.

just if your wondering, this is said car with troubles.

[copmagnet]

I had a hard start issue for several months with my SR. I did a lot of checking and finally found the culprit to be the fpr. The Walbro was overpowering the stock regulator, it was sitting at roughly 55 psi at idle instead of 43. Way too rich. Ended up ruining the injectors, so when the car was turned off it bled past them and into the cylinders. Replaced injectors, put a good aftermarket fpr on it, set to factory psi, starts perfect every time. Plus, its an easy check: borrow a gauge, pop it on. If its too high, could be the issue. Just an idea, hope it helps.

[Mountain_Man]

i tested the fuel pressure cold and it was at 40 psi with the old pump. ill have to check it with the walbro. but i have previously own the motor and i used a walbro and it ran fine. the guy i "sold it to"/"bought it from" had to use a red top ecu which is tuned for a different motor.

fortunately tonight it started after sitting for about 15 mins. tonight also marks a year that i have had the car. im still getting a harness and ecu for it in due time.

[Mountain_Man]

car is running toooo rich. the car is flooding out when its hot and causing it not to start when its hot. just if anyone is wondering.

anyone have a black top ecu and harness?

[R@ddy]

Yupp. Found my problem. My fuel pressure was at 55psi instead of 35 lol

[Sileighty_85]

stock FP is 42psi

[R@ddy]

42 with vaccuum, 35 without.

[KiLLeR2001]

SR20DET... 43.5psi without vacuum. ~37psi vacuum plugged in.

[R@ddy]

Ahhhh that's what I meant

[240sx-pat]

What do you guys mean without Vacuum? you mean without a vauum hooked up to the FPR???

[Kingtal0n]

As a temporary band-aid, if the ECU is injecting too much fuel during cranking (and causing a flood-no start situation) simply hold the throttle to the floor, this will "CLEAR FLOOD" mode in the ECU, causing the injectors to stop injecting fuel, and the OPEN THROTTLE BODY will allow full airflow to the cylinders, allowing any flood to clear out, and it should start like that.

The ECU watches TPS for the clear flood, so if the TPS is not working right the ECU will not "clear flood" mode. However, the fully open throttle body will still allow a flood to clear and the car to start-- unless its ALOT of fuel being injected (as with LARGE injectors).

The engine with start with about 9-12ms of fuel from COLD start, but it only wants about 5-6ms of fuel during a warm start (OEM INJECTORS!). or less, depends on the engine. Engines with big cams may require less fuel to start, since cranking airflow may be higher but consequently compression, is usually lower, some fuel may be wasted to the exhaust, It depends on how the IACV is set to allow air in, and whether the OEM IACV has the warm coolant wax expanded or not, and how the throttle body is set (holding water or not?)

[240sx-pat]

I'm having a hard time adjusting the fuel pressure.

would I just need to turn the key on to check the fuel pressure ? and make sure that it reads 37 PSI and once engine is on make sure it reads 43?



because if the car is on and I unhook the vacuum hose while it's running my car will die.

[KiLLeR2001]

When you unplug the vacuum hose from the FPR it should read around 43psi, the car should NOT die, it'll idle rougher but if its dying then you may have other issues.

edit: When pulling off the vacuum hose you can cover it up with your finger if that helps any.

[240sx-pat]

Originally Posted by KiLLeR2001

When you unplug the vacuum hose from the FPR it should read around 43psi, the car should NOT die, it'll idle rougher but if its dying then you may have other issues.

edit: When pulling off the vacuum hose you can cover it up with your finger if that helps any.

Yea, if I cover it up it'll continue idling fine.

So here's what happening I turn the car on let the car warm up and I set it at 36-37 psi while the vacuum is on , if I take the vacuum off I'm at about 46 instead of 43.

I have tried doing it the other way also , if I adjust it with the Vacuum off and set it at 43 and hook the vacuum back up I'll be at around 32-33


I can't seem to add 37 and 43 together

Will it be safe if I left it at 36-37 with vacuum hooked and 46 when unhooked? or is this unsafe for my car?

[KiLLeR2001]

Adjust it at 44psi when vacuum unplugged, plug it back in and see how it drives.