Hard to start (COLD)

[87mk3t11]

Hey everyone i just recently joined SupraMania and its a awesome website, lots of good information.
Recently I just picked up a 87 mk3 supra and put a jdm 7mgte in because the other one had a rod knock from previous owner. The problem i am having is when the engine is cold it takes about four cranks to start (each crank goes for about 2 seconds). When i turn the ignition to the run position with engine off i do not hear the fuel pump coming on. But when i am cranking the engine i hear the fuel pump going on. When the engine is warm it starts up first try with no problems. If anyone has any suggestion on what this might be your info would be greatly appreciated.

 

[92turbo4life]

strange.... mine used to do that but now when i start the car i give it 2 pushes of the gas pedal when the key is turned and it will start otherwise it will take about a 5 second crank if it has been sitting for a while.....

 

[jetjock]

You won't hear the fuel pump when you turn the key because of the "circuit opening relay" (COR) that is controlled by the ECU. Like all modern EFI systems there must be a way to shut the fuel pump off in the event of a collison. Many cars use a switch in the AFM but the turbo Sup uses the COR. Basically it serves the same function of the old Bosch RPM relay used in many Volvos and German cars. When the ECU senses engine rpm during cranking it closes the COR and energizes the fuel pump. Lose engine rpm with the key on, say in the event of a collision, and the ECU will shut the fuel pump off. Btw, if you can hear the fuel pump during cranking you either very good hearing or a very bad fuel pump

Hard cold starts are usually associated with the cold start injector (CSI) or it's thermo time switch (TTS). The TTS and CSI both receive power only when cranking. It's a pretty simple circuit so start there. Btw, most CSIs I've seen are pretty gunked up so you might want to pull it for a cleaning. Fwiw your problem doesn't sound too bad so I suspect a gunked up CSI. That it starts OK warm is an indication the fuel system rest pressure is holding so I'll put money on a bad TTS, dirty CSI, or a wiring problem. Course, hard cold starts can be caused by other things too but I'd begin by looking at the system that is there to prevent them.

92turbo4life: Not that I'm doubting you but on EFI systems using pedal should do nothing to help start the engine. You likely have a minor problem somewhere but it sounds like it's
not worth chasing.

 

[GrimJack]

Considering you just swapped engines... mind if I suggest checking that your CSI sensor is plugged in? It's at the top of the thermostat housing, usually a two wire green plug if I recall correctly.

 

[87mk3t11]

Alright i appreciate your input, would anything with the fpu vsv have anything to do with hard starting? because i wasnt sure about how to hook it up, i printed out some of the vacumn diagrams from the web site and going to hook that up tomorrow after work. and i am going to pull out the CSI and give it a good cleaning!

 

[jetjock]

FPU VSV is only active for hot starting (ECU looks at the coolant sensor). Without pulling my TCCS books out I'm gonna go out on a limb and say coolant temp needs to be above 130 F or so for the FPU VSV to become active. You have cold start problem.

While you have the CSI out for cleaning apply 12 volts to it while spraying some solvent into the inlet. That'll verify the valve is working and help clean the orifice. If you can't do that at least ohm out the coil and soak the tip in solvent (keep the solvent away from the coil). After you clean the CSI and reinstall it, be sure the car is cold and hook a 12 volt test light up across the CSI connecter. See if the test light lights during cranking. If so you're good to go. If not, jumper the connector on the TTS and repeat the test. If you get a test light then the TTS is bad. If not, the wiring to the starter circuit is open.

Remember, for the CSI to work the engine must be cranking and the coolant must be cold. In any event, CSI operation will cease after 8 seconds or so even if cranking is continued. It's called a Thermo "Time" Switch for a reason

 

[boltz]

I have a quick question regarding the CSI.

Where is the timer circuit located?

I know where the CSI is
I know which thermo sensor is for the CSI
is the timer circuit integrated into one of these or is it alse seaperate?
TSRM is kinda vague on where the timer is.. the wiring diagram shows it seaperate.

TIA

 

[mrnickleye]

The sensor in the coolant system on the thermostat housing has the timmer built in. It's actually just a heat sensitive switch that stops completing the circuit when it reaches a pre-determined temp, which is caused by an electical heating element inside the switch.

These units are not cheap, and are Dealer only.

 

[boltz]

what causes this 8 second thing i remember reading? if this thing is only temp sensitive not timer...

 

[DaSuprawolf]

My 88 N/A starts like that too, but im not to concerned because it turns over at normal speed, and really, your building oil pressure when cranking too so its good for starting, it useally takes a few seconds to build presure, so if it started right away, you'd be running for a second without oil pressure.

 

[boltz]

only reason for me asking my questions is because i have a 7m swap into another car and i just want to make sure i am not missing part of the CSI circuit... as long as it is all part of the motor wiring harness i am good.

 

[johnathan1]

ugh, my car's doing these exact same things... Would a broken ECU temp sensor, (no signal) cause hard starting when cold? How do you clean the CSI?