Thread: Hard Start When Warm

I did the test for several minutes and nothing came out. So I supposed it passed this test then?

That's exactly what I did.

So I am running a bunch of other tests. Ever since I did my own head gasket I have been paranoid that it didn't seal, just because it was a huge job for me and I've never done something that extensive. Anyways, so I had been watching my coolant like a hawk, and for several months it didn't go down. Then one day several weeks ago the level dropped slightly. I finally got around to doing some tests along with this test you told me. I did a cold compression test and I'm curious what your thoughts are on these numbers. I actually found a leak with the radiator pressure tester, so that may have been the problem, but I digress.

C1 172
C2 162
C3 175
C4 172
C5 170
C6 173

Cylinder 2 is what has my attention, because well that's where I have a feeling it would start leaking at. When I was torquing down the front head towards that side I wasn't as careful as the rest because someone was rushing me...

Alright, so I grabbed a fuel pressure gauge to do some more in depth tests with the fuel system since the fuel pressure regulator came up for the hard start issue.

Here are my results on a bone cold car:

-When I turn the key while the pump is priming the gauge goes to 56psi.
-Immediately after the two seconds when the fuel prime prime shuts off the gauge drops to 49psi.
-After 10 minutes the gauge has dropped to 43psi.

Plan is to let this sit overnight and see what it says in an hour and then in the morning. Then I will continue with the engine running test with the cold start and pull the line from the FPR as well. In a few days I will also do a hot engine prime, start, and FPR test. The car is partially apart right now in the garage for some other stuff so I can't drive it right now.

I'm using this PDF for my reference which says the prime should be between 52-59psi: https://www.google.com/url?sa=t&rct=...EyzTfaexkx7Tsw

However, I am a little confused as to which reading I should compare that to. Should I compare that value to the prime pressure of 56 or the pressure immediately after of 49? The reason why I ask is because I am following this troubleshooting guide for GM fuel systems http://www.fastfieros.com/tech/fuel_pressure_L67.htm. I know it's not for my specific engine, but it's for a 2000 Grand Prix with the 3800, so even though the exact values may not hold true, the diagnostic procedures should be pretty much the same because the fuel system setup is similar. In this specific guide in step 2 it says to observe the pressure with the fuel pump running and compare it to the specification (which matches the guide I gave above for that engine). Then in step 3 it says the pressure may vary slightly when the pump stops running, but to note the pressure after it settles out. Then start the 10 minute countdown and watch for a 5 psi drop from that value.

Anyways it looks like I pass the initial prime test, but slightly fail the leak down test. I don't have the shut off valves, so where the fuel is leaking I cannot determine. I'm definitely not going to crimp the brittle plastic lines to find out! Maybe this is something to follow for my hard start issue or rough idle issue after all? I'm questioning leaky injector because my long term fuel trims are pulling fuel at like -15 at idle if I sit long enough, but fine everywhere else.

Also, as a side note, I'm pretty sure I found where I was loosing coolant. Let's just say I'm never using those stupid worm drive hose clamps again. I have learned my lesson. I replaced two crimp style hose clamps with the worm drive types, just because I hate the crimp types. Well the damn thing had loosened slightly and when I pressurized the system it started leaking. I happened to still have the crimp style clamps in my tool box, so I put them back on. Now the radiator pressure tester seems to be holding pressure well. The gauge doesn't seal perfectly to the radiator, but the loss over the past hour has been under 1PSI. I'll still warm test it, but it is definitely a relief to actually find an external leak that was an easy fix.

Funnily enough, several weeks ago I did some work on my gf's Aveo and I put the worm drive clamps on all of her hoses. Not even two days later I had to tear her system down again and dig all of the crimp style clamps out of the trash and put them back on because half of the worm clamps were leaking like crazy. I tightened the hell out of them btw. At the time I thought to myself "Man I need to check these on my car" and then forgot about it...

Yeah I used the hardware store type, not the auto parts store ones.

Anyways, an hour later the fuel pressure gauge is at 32psi, will report the overnight result tomorrow. Any thoughts? Am I leaking somewhere or is this bleed down normal?

The fuel pressure was 28psi after two hours and has bled out entirely overnight. Still unable to rule out a leaky injector without more tests. Basically trying to figure out the hard start and high negative ltft's with misfires while idling.

On a positive note my coolant pressure only lost 1PSI overnight. The seal between the gauge and radiator is really poor and even the slightest movement will cause it to hiss there, so I'm betting that's where that loss was. I don't think I am leaking coolant internally like I was fearing previously after my head gasket and intake gasket replacements.

However, I think at this point I should just bite the bullet and send my oil to Blackstone. That will be the definitive test of fuel or coolant in my oil showing internal leaks. Luckily Blackstone is in Fort Wayne, which is my hometown, and I will be traveling there shortly so I can drop it off in person.

Interesting tidbit about compression testing. I always hear the 10% as the maximum difference between cylinders, but it looks like GM allows up to 30%! I feel like that would easily be noticeable in the drivability of the car. Check out the service manual page I found:

http://workshop-manuals.com/pontiac/...ons/page_2480/

Well I was able to get my hands on a new fuel pressure regulator for a decent price, so I said screw it and swapped it out. It didn't solve any of my issues. Hard start still exists, fuel trims are still extremely negative, and misfires still occur at idle. So it has to be something else.

Originally Posted by Scottydoggs

just how neg is the long term fuel trim? as far as stock goes they can see -15 and be normal.

screen shot of the t app when i was stock still. nice hot summer day. 111º imtake temps....thats hot. lol

What scanner app is this?


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Torque App is what I use as well. Mine seems to max out at -11 at idle. I can't be sure it's just not a consequence of my random misfire issue at idle. But I was at least hoping the hard start issue would resolve with the FPR, then I could finally tick something off my list.

Yeah I would expect it to see a lean condition if there was a vac leak. Damn, just at a loss for what these issues could be.

Well I did the warm compression test and all cylinders were 180 to 185. So that's good. I ended up breaking one of the spark plug wires so I had to replace the set again. Still have the misfire. However, I think MAYBE the new fpr may have cleaned up my hard start issue. I'll still need to drive it for awhile to confirm for sure though. I'll post back on the matter after I have driven it for a few weeks.

Alright I have been driving it for awhile. It seems that the hard starts have cleaned up quite a bit. I used to get them pretty frequently, but now I only get them rarely. I will say that its still pretty cold right now, so I'll know for sure when it starts getting hot outside again.

I also got the Blackstone report. No antifreeze or fuel dilution after 2500 miles on the oil change. But the copper was insane at 43 (compared to 10), lead was elevated at 11 (compared to 5), and silicone was insane at 100 (compared to 15). Blackstone said it was because I had done extensive work to my vehicle, which is crazy they could tell because I did and I didn't tell them at all, and that they hope to see those numbers come down next time. Black silicone was used for the end caps on the intake gasket. I did get a sample from the very first amount that came out of the engine like a noob, so that may have been why it was crazy too. I guess I was supposed to let some pour out for a second first.

I know it's been quite awhile since I last reported, but it is hot outside and unfortunately today I got another very obvious hard start. While it seems to be less frequent, that might just be wishful thinking. The FPR probably wasn't the culprit.