Tanker5503

Just started happening today twice to me already. Went wheeling yesterday, let the truck sit overnight and go to start it in the mourning and takes alot longer to start then normally. went to start it ~ 4 hours later and it did the same thing. i don't smell any fuel under the hood (yet) and it runs fine. Fuel pump or small fuel rail leak somewhere im assuming? 88 4runner and the rebuild has~7K on it 252k on rest

Any leads be great Thanks

Tanker5503

update

so i let it sit for last 5 hours and opened up the air filter and filled up the lines in the rails (ignition on) it started up right away after tbat. i don't smell any gas around the engines at all still i put my hand by the dampener and don't feel any gas on it

Tanker5503

update

when i have a full tank of gas it starts fine no problems but i notice it getting harder to start as the gas level reaches half when sitting for a 5-6 hours its a long crank start. Im going to order a fuel pump by the end of this week most likely just to start somewhere with fixing this.

scott90

Coolant temp sensor or the cold start injector switch

Sportsmanphil

Fuel pump is leaking line pressure back into the tank.

Cycle your ignition off-run-off-run-off (hold on the run position for about 3 seconds before going back to off) and then try to crank it. If this solves your problem you can fix it with a new fuel pump. Or just cycle your ignition once/twice before cold engine cranking.

Keep in mind, if this is the case and you dont replace the fuel pump you will replacing a fuel pump and an ignition switch in the future ;-)

sb5walker

Takes two things for the fuel to run backwards into the tank: a leaking check valve in the pump and a leak - external or internal (injector) - that allows air to be drawn into the fuel lines as the fuel drains back down into the tank. Since you don't have a fuel smell, it's probably a leaking injector (or possibly the fuel pressure regulator that may allow air to be drawn from the return line). If it's an injector, it's probably not just leaking air, but also leaking fuel when fuel lines are pressurized. You could inspect plugs, looking for a rich one (flat black deposits) if you wanted to try to identify the culprit. You can try to fix the injector by running a PEA injector cleaner (Red Line SI-1 Complete Fuel System Cleaner or CRC's "Guaranteed to Pass Emissions Test Formula", but probably you'll need to send the injectors to witchhunter to be sure.

The fact that the fuel drains back less when the tank is full is either due to there being less compressible air, so even though the check valve is leaking, there's no room for fuel to drain back down, or due to the level of the fuel being higher so the fuel in the line only leaks down to the level of the fuel in the tank. I would send all the injectors to witchhunter, then see how you make out, before bothering to replace the pump. Even with a leaking check valve it may still be pumping fine, and with the top side leak(s) taken care of, the fuel may not drain back into the tank - it'll act like a straw when you hold your finger on top: the coke won't drain out so long as you make a good seal on top.

BTW cycling the ignition switch won't run the pump. The circuit opening relay is only triggered by the ignition switch in the START position when actually cranking, and then is triggered by the fuel pump switch in the air meter. You could tap into the FC wire and put a switch between it and ground which will run the pump when ignition is on, but that still leaves you with a leaking check valve and worse, probably a leaking injector. So I would fix the top side leak for sure, and possibly also replace the fuel pump with an OEM Denso if necessary. autohausaz.com has great prices on fuel pumps with kits (sock etc.) (no affiliation with them).

Tanker5503

ok cool thanks for all the info ill go buy a thing of crc first and i guess fill up with chevron to see if miracle in a bottle works. if not ill replace the fuel pump. don't really want to tare apart my throttle body agian but will probally do so it if still a leak

sb5walker

The CRC product only has about 30% PEA, about two thirds of the Red Line. So you might consider using 1 and a half bottles of the CRC in a full tank, then use the remaining half bottle in the next fillup. Try to burn the gas fairly soon (within a day or two at the most) since PEA can soften the nylon sock on the fuel pump if left in too long. But no other in-the-tank product cleans injectors anywhere near as well.

Sportsmanphil

SB5 is correct on cycling the ignition switch. That will only work for the Tacoma style fuel pump, so ignore my last suggestion to try that.

If your injectors are leaking into the cyls, I would imagine you will get a nice rich puff of smoke from the exhaust once it fires up.

Tanker5503

so i replaced the fuel pump with a denso one and also found another cold start injector around and put it on and its still doing the same so ive narrowed it down one of the injector are possibly leaking.
still is only happening with i get below half a tank of gas

sb5walker

.....

Tanker5503

i started with the pump for peace of mind for it having 260k on it. and its my DD and wont have another car to use for a few days untill next week

Codytr1

Thanx guys I was having the same trouble with mine. Ill try o-rings this weekend

redhanded

ditto on the o-rings. I had a 90 pickup that had the same problem. changed my injector orings, and it helped a bit.

Yotainmyblood

Hey man, did you ever find what was causing your hard start condition. I'm in the same boat. It seems mine is leaking fuel back down the line. I can put a wire jumper in to activate the fuel pump and then turn the key to on and wait a few seconds and then it will start right up. But if I just try to start it as normal, it takes forever. I replaced my fuel pump,cause I thought it was the check valve, and that didn't help. I even changed it four times total. I used a used one first, then brought a cheap one and then got two different new denso pumps. Cause in the middle of changing them ,I replaced all my fuel injectors. That didn't help so that's why I tried another pump. But now that it's cold, it's taking alot longer, and now I found I had to replace my cold start injector time switch. After that I found it was actually the harness that plugs into that csi. But now I got all that replaced. And I fired it up and it ran for 4 seconds and died. I think it was because I had two of the ac idle up hoses backwards cause I switched them around and it finally fired up and ran. I'll find out tomorrow if the cold start injector switch was the problem all along. Cause before I started to replace it, my problem was that I could let it sit over night and go to start it and I would have to crank it for about 20 seconds. But once I got it started, it would start right up anytime I would crank it. It was just when it sit overnight that I had this problem, and I thought it was because there was no fuel pressure in the rail until I cranked it for awhile. So I was thinking that fuel was running back down the fuel line. I even went out one morning, and before I cranked it, I loosened the banjo bolt on the fuel rail and it didn't leak out any fuel. And I know my other truck, when I do that, it will squirt out fuel, even after it sits for a week. So that's why I think fuel is leaking back down the line. But I've replaced both things that would let that happen. Unless there's a hole in my fuel line,and I've looked it all over for a leak. So did you find your culprit?

Codytr1

If I remember correctly the o-rings did the trick. I never replaced the fuel pump on that rig.

Yotainmyblood

Ok, thanks for the reply. I've checked my orings when I replaced the injectors or even replaced them. I'll probably take my fuel rail off and take a hard look at where the injectors plug in and see if I see a crack or something. I pressurized the system with the plenum off but I had to hold my finger over the FPR and I didn't see a leak. But I had already had gas everywhere and didn't keep it pressurized very long. So maybe it's time to rig up another line to go back to the return line from the FPR and spend some time with it pressurized and maybe I'll find it.

Codytr1

It been awhile since that issue. But I think I also did something with the flat washers on rail too. I wish I could recall more details for you.

2ToyGuy

You do know the FSM only specifies about a 5 minute hold time for fuel pressure, yes?

And no matter WHAT, you really never, ever should drive with the jumper in holding the fuel pump on. It's just asking for an engine fire to do that. The COR, and all the rest, is a very important safety system.To bypass it is asking for trouble. Accidents happen when we least expect them, and most often on short trips, locally. Loosing your truck is one thing, burning alive before the First Responders can even arrive is an entirely different animal.

If you are really concerned about having pressure in the fuel system before a dead cold start, just turn the key to start for a few seconds before pressing the clutch in, or pressing the Clutch Start Cancel switch. You can hear the fuel pump run, and when it's tone changes, press in the clutch. It'll fire right up. I do that in my 87 4Runner, works like a dream.

Anywho, good luck, and have fun!
Pat☺

Yotainmyblood

You probably replaced them. Your supposed to when you take em lose. I replaced mine halfway through messing with all of this. But i think i got it taken care of. I replaced that cold injector time switch and it still wasn't spraying and i noticed that plug on the cold injector , when i looked at inside where it plugs into those prongs, one side i couldn't see the contacts that fit over the prongs. So i stuffed a piece of wire in that one side and presto, it started spraying. So i put it back together and it cranked right up. So i let it sit over night and it cranked up pretty quick the next morning. And this morning it cranked up after about 4 seconds, and its about 25 degrees this morning. So maybe the cold start injector was the problem the whole time. And if thats the case, then it helps with starting all the time. And fuel will stay in the rail, but it doesn't have pressure after sitting overnight. Some people say the cold start injector only sprays when its a certain temp or cold. But i bet it sprays at any temp to help with start up. Or maybe not when its hot, but after it has sit all night, its supposed to spray. But the time switch probably wasn't even bad, it was that harness the whole time. I tested the injector with 12volts, and it worked, so i thought it was the time switch. But it was the plug. Lesson learned. And learned about how that thing works for myself, cause you wouldn't know if you listen to people say it only sprays when its real cold outside.