Long Hot Start
01-17-2013, 11:28 PM
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Long Hot Start I had this posted in other section, but I've been told that it really belongs here. Can anyone give me some advice?
So, recently my car has been progressively harder to start whenever it is warm. I do not think the starter is getting heat soaked, because it spins at the same rate as when it's cold. I measured the fuel pressure at the rail, and it's getting 56lbs at prime with only a 2 to 3 lb decrease at start. The fuel pump, a walbro 255, is sounding very obviously different sometimes: sort of like its strained. That's what got me thinking that it may be a fuel issue. The car will start when hot when I play with the throttle pedal. Any ideas?
So, recently my car has been progressively harder to start whenever it is warm. I do not think the starter is getting heat soaked, because it spins at the same rate as when it's cold. I measured the fuel pressure at the rail, and it's getting 56lbs at prime with only a 2 to 3 lb decrease at start. The fuel pump, a walbro 255, is sounding very obviously different sometimes: sort of like its strained. That's what got me thinking that it may be a fuel issue. The car will start when hot when I play with the throttle pedal. Any ideas?
01-18-2013, 03:50 AM
#2
A heat soaked IAT sensor can make it harder to start. The original tuning was biased too much to the IAT over ECT. This can certainly be tuned out be a good tuner. I relocated my IAT sensor further away from the engine but still in the intake track and it helped a great deal.
01-18-2013, 03:26 PM
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On the LS6, wasn't the IAT integrated into the MAF?
Ninja Edit: How well did the 102 fit under that hood? I've heard some conflicting things about fitment issues. I'm trying to decide between the 102 and the 92. Thanks for your reply!
Possible Solution?: So, I went for a longer drive tonight, [~30 minutes], and I came home, put the car in the garage, let it sit for a couple minutes, tried to start it and started up without any issue whatsoever. Then, I began listening closely to the fuel pump as I primed it on different occasions; sometimes it would sound normal, other times it would sound very strained. I noticed that whenever I tried to start the car after this "strained" fuel pump primes, it wouldn't start as easily. So, I'm ordering a new Walbro 255 to see if this does anything. It's inexpensive enough, and the pump is actually a MKIV supra pump, which I'm sure will be going out any time now anyways. I'll keep you updated.
Ninja Edit: How well did the 102 fit under that hood? I've heard some conflicting things about fitment issues. I'm trying to decide between the 102 and the 92. Thanks for your reply!
Possible Solution?: So, I went for a longer drive tonight, [~30 minutes], and I came home, put the car in the garage, let it sit for a couple minutes, tried to start it and started up without any issue whatsoever. Then, I began listening closely to the fuel pump as I primed it on different occasions; sometimes it would sound normal, other times it would sound very strained. I noticed that whenever I tried to start the car after this "strained" fuel pump primes, it wouldn't start as easily. So, I'm ordering a new Walbro 255 to see if this does anything. It's inexpensive enough, and the pump is actually a MKIV supra pump, which I'm sure will be going out any time now anyways. I'll keep you updated.
Last edited by treefingers; 01-18-2013 at 08:49 PM.
01-22-2013, 05:13 PM
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Update: it isn't the fuel pump, and the car isn't starting at all anymore. Battery is good; doubtful that it could be the alt. I'm thinking its an electrical issue, nevertheless. When I tried to test the battery while it was in the car, sparks were generated on both of my multi meters prongs. Before this, I was ready to pull my heads to get them ported, but now all of this. So, I'm ready to get this thing together. In between work and school it's just hard to find time to mess with it.