93 Laser

[CrackedDSM]

Hot start? What chu talkin bout Willis?

 

[DreamChaser7]

Hot start? What chu talkin bout Willis?

I wanted to but..nah

 

[dwb]

My experience is the FPR solenoid is beneficial for cold starts. It increases base fuel pressure when the intake is under vacuum. I have my solenoid hooked up but still deal with the hot start issue.
That being said, I think you have your solenoids backwards. The FPR solenoid is the one on the right with a vacuum/boost source on the front. The left one that you have hooked up in your last pic is for the EGR.

 

[Stapl3]

edit: You're right! I did use the wrong solenoid. Thanks tons for pointing that out.

This is what I settled on for understanding the FPS's purpose:

HOW THE FPS WORKS:

Those of us that have set our own fuel pressure should have noticed that you need to disconnect the vacuum line from the fpr when doing so. You can achieve the same affect using DSMLink and activating the fuel pump with the engine off. Ether way, the point is to assure that there is no vacuum seen at the fpr while you set its base fuel pressure.

-- A solenoid, like the one in our fps, does one basic thing: open or close when activated by and electric field. They are used to control the flow of a confined system like the vacuum line running from our IM to our fpr. The DSM fps is naturally open. When it is activated by the ECU it closes.

-- The fpr does three basic things: control fuel pressure, allow fuel pressure to be user adjusted, and increase pressure, pound for pound, during boost conditions.

A side affect of this pound-for-pound fuel pressure increase is that there is a fuel pressure decrease under vacuum conditions (i.e. idle or star-up conditions). This is why you disconnect the vacuum line in order to set base fuel pressure.

It is this function that the fps utilizes in order to increase fuel pressure during hot-start conditions. Mitsubishi noticed that a hot car would heat the fuel lines running near the engine to a point that when you re-start the car without allowing it to cold down the fuel can evaporate as it travels to the engine. This condition made it hard to start the car.

In order to combat the Hot-start condition, Mitsu added the fps to the vacuum line between the fpr and the IM to block vacuum from reaching the fpr during hot-start up. This has the same affect as disconnecting the vacuum line and increases fuel pressure, as seen at idle, by about 6 psi (or back to base pressure).

When the ECU sees a hot-start condition it activates the fps by switching to ground, completing the fps circuit and activating the fps. The closed solenoid closes the vacuum line running from the IM to the fpr in effect removing a vacuum condition from the fpr.

 

[dwb]

Normally open is right. Here's mine, and I'm 100% sure that's the correct solenoid. My dsm was bone stock when I got it.

A-15

 

[CrackedDSM]

I wanted to but..nah

I am not afraid to look like an idiot and ask a dumb question. Never fear.

 

[DreamChaser7]

I am not afraid to look like an idiot and ask a dumb question. Never fear.

I think more like I probably already asked this question or read it somewhere and just forgot. I’ll retain much more once I do it once with my own hands.

 

[Stapl3]

It's not a stupid question, rather it's stupid easy to search the entire internet for 'dsm hot start'. But I'll entertain it. Basically what I'm experiencing is starting the car and let it warm up, take it out for a cruise and a pull, then park it to do laptop work. 20min later I go out and the car just cranks. I'll use my right foot to get it started and it just seems like it's running on 3cyl but it's not. It won't freely rev, it hesitates bad before revving good, and when I let off revving it falls below target rpm - to recover - but just overall sucks.

I don't see a 100% absolute smoking gun answer online to fixing it. The theory is the rail gets hot and it vapor locks. Ive tried cycling the pump. FPS solenoid as I posted, jury still out on that. Next I'll probably try the CAS off the parts car as I know that is controlling the injector phase angle. Maybe a different TB is in the cards for me, and I still have to mess with the S wire to potentiometer for stronger voltage. I'll keep chipping away at it but this is lousy to incur.

 

[CrackedDSM]

It's not a stupid question, rather it's stupid easy to search the entire internet for 'dsm hot start'. But I'll entertain it. Basically what I'm experiencing is starting the car and let it warm up, take it out for a cruise and a pull, then park it to do laptop work. 20min later I go out and the car just cranks. I'll use my right foot to get it started and it just seems like it's running on 3cyl but it's not. It won't freely rev, it hesitates bad before revving good, and when I let off revving it falls below target rpm - to recover - but just overall sucks.

I don't see a 100% absolute smoking gun answer online to fixing it. The theory is the rail gets hot and it vapor locks. Ive tried cycling the pump. FPS solenoid as I posted, jury still out on that. Next I'll probably try the CAS off the parts car as I know that is controlling the injector phase angle. Maybe a different TB is in the cards for me, and I still have to mess with the S wire to potentiometer for stronger voltage. I'll keep chipping away at it but this is lousy to incur.

Not being a smartass here, I promise, but have you TRIED searching Google for anything now? I used to be a guru at Google fu, now I can’t find shit.


But, that’s so weird. I’ve never had that issue. Legitimately never. That sounds frustrating for sure.

 

[dwb]

It's not a stupid question, rather it's stupid easy to search the entire internet for 'dsm hot start'. But I'll entertain it. Basically what I'm experiencing is starting the car and let it warm up, take it out for a cruise and a pull, then park it to do laptop work. 20min later I go out and the car just cranks. I'll use my right foot to get it started and it just seems like it's running on 3cyl but it's not. It won't freely rev, it hesitates bad before revving good, and when I let off revving it falls below target rpm - to recover - but just overall sucks.

I don't see a 100% absolute smoking gun answer online to fixing it. The theory is the rail gets hot and it vapor locks. Ive tried cycling the pump. FPS solenoid as I posted, jury still out on that. Next I'll probably try the CAS off the parts car as I know that is controlling the injector phase angle. Maybe a different TB is in the cards for me, and I still have to mess with the S wire to potentiometer for stronger voltage. I'll keep chipping away at it but this is lousy to incur.

Hot start has always plagued me in a very minimally modified DSM, with the FPS hooked up. I've heard the theory of fuel vapors/hot fuel rail, but hard to prove/disprove. Although it seems like running the pump would flush the rail with fresh, cool fuel, IDK. Another theory I've heard is an injector or multiple injectors leaking into the cylinder and causing rich conditions. I've been trying to watch my AFR when it happens and the few times I've caught it, it does seem pretty rich.

 

[Stapl3]

After sitting for a long weekend, I cranked it and it started and ran strong. It idles so well. I bothered to log, and use, TPSdelta for once and used that to rather aggressively adjust the tip-in in DA along with aggressively adjusting the timing cells just off idle. Wow. What an adjustment. It revs so clean and fast when I punch the throttle. I can't believe this is a DSM.
Then I let it warm up, turned it off, and let it sit for 30min. And you know what's next. Crank crank crank crank, stumble, crank crank, right foot, come to life awkwardly. Probably an injector problem there, but after it runs it's still crummy. I think voltage is a big variable, so I'll mess with that S wire to potentiometer tomorrow, fingers crossed for always 14+v. Maybe that's the silver bullet?

-

This weekend I had more time than ever to relax and think about things. Final thoughts: The CAS also controls the pivot angle of the injectors which I think is an issue assuming how oddly my CAS is physically adjusted to obtain 5*.

While cranking, it's hardware only. There is no software involved. A week ago when the CAS was wrong at 10*, the car would fire instantly. Half crank, 1/4th second, fired up. It was so rad and I wanted to leave it all alone. How can I have that cake and eat it too?

Next thoughts: If the CAS is 10* advanced when it should be 5* I can put all the timing sliders down 5*, to globally adjust, and it cancels itself out with zero repercussion and is applied at all times. I can have that amazing start with timing "wrong", but a split second after that be what is typed in 'link. This is super big time. AND I can now have my way with the fuel injection pulse timing. A new door has opened.

I love that I have so much of my interest and time into 'link and it still provides me with things to challenge me and learn allowing me to come up with new stuff on my own. It's an awesome feeling to cut a new path on a 30 year old platform.

 

[Stapl3]

So I guess the alternator gave up the ghost on me and is why I have been having "hot start" issues. At idle I get like 11.8v now, I can free rev it up to 2-3k rpm and it will output into the 13's, but at WOT it goes from 12.5 to upper 11's throughout the pull. Messing with the S wire every which way possible did absolutely nothing. I found this pulley which would spin the alternator 11.5% faster, but I don't even think that would help out my idle and certainly would do nothing for WOT. Maybe hooking up the F and L wire to 12v was wrong. Maybe the alternator is just a dud. Pretty defeating as this will be the 3rd alternator now in about 10 miles of driving.

I will probably pull the power steering lines, pump, and canister off my parts car so I can install those when I pull this alternator out.

 

[1cleangsx]

That sucks, I’m running a 90amp from advance auto with good results so far, 14-14.2 at idle and 13.3-13.4 at wot. I will be upgrading to a 2gauge wire feed at the power/b terminal for hopefully even less voltage drop at wot, but I’m thankful I got a Good one , alternators seem to be hit or miss no matter the brand or where there from

 

[Stapl3]

The crummy part is I was so happy with how it was working that I bought two more identical units for my other cars and now I'm here wishing I didn't so I could alteast switch up brands. If these two do the same thing it'll be a very very defeating path to figuring it out.

I do have a new Mitsu unit here along with a known working 160amp motor city unit with a pulley I spent too much time figuring out that I could put in instead, but man I wanted mid 14v across the board sooooo bad.

The Rube Goldberg in my brain wants to replace the battery with a tray of Dewalt/Milwaukee tool batteries, somehow reducing their output to 14.5v, and just run a whatever alternator to soften their drainage of power.
I guess ultimately I hate that we use a 12.5v battery and rely entirely on the alternator to pick up the slack.

 

[1cleangsx]

Dude I’d say if your not losing fuel pressure at wot or having trouble hitting target AFR’s who gives a Sh!t

 

[Stapl3]

Dude I’d say if your not losing fuel pressure at wot or having trouble hitting target AFR’s who gives a Sh!t

Nah youre looking at it wrong.
Weak spark, injector behavior, restarts barely happening, bogging on rev down, throttle response, not trusting it, etc. I could probably make quite a list. Constants over variables on everything is what separates a great functioning car from one that disappoints all around with spare glimpses of success here and there to distract.

I want X voltage at all times and I'm gonna pursue it until I get it. The by-product is learning along the way. The process can suck and to an outsider you're just failing repeatedly.
Meanwhile if everything just worked we'd learn nothing and these forums wouldn't need to exist.

 

[1cleangsx]

Damn. I stand corrected. I hope you get’er figured out, I’m sure you will

Reading your previous posts it is a puzzled situation. I never have any hot start issues. Whether I’m firing the car back up after topping it off or starting it back up when leaving the gym. My set up is relatively simple, ecmlink v3 speed density, pump e85, 2150’s, no isc/fiav, so I have to baby the throttle on first start for 5-7minutes till it goes into closed loop, then when the motors warm maybe 30 seconds or so but no issue at all firing it up, it gets fuel,spark and boom it starts

Hopefully if my test drive goes well tomorrow I’ll post up a hot start log you can pick apart, I’m sure it’s something simple you’ll figure out

 

[99dsmer4g63]

If you seriously want to use dewalt batteries you should look up some reducer bucks on google.

I use one in my job trailer so I have lights and stuff when my truck isn’t hooked up to it. I’ve also used them on my daughters battery powered toys. I also used one for my buddies fuel cell pump.

-Daniel