I'll report all fuel tests Monday...Thanks

 

Fuel pressure test reports:

Key on/engine off 59-60psi (hits 60 as soon as key turns, then immediately backs off to 59 and stays)

Engine idle 54 psi, constant
engine rev 56-60psi
turn engine off 61psi

leakdown tests as follows...

first test...

minutes / psi

1 / 59
2 / 59
3 / 58.2
4 / 56.4
5 / 56
6 / 55.8
7 / 52
8 / 53
9 / 52.5
10 / 53

second test immediately after first test

minutes / psi

1 / 60
2 / 60
3 / 59.5
4 / 59
5 / 58.5
6 / 58
7 / 57
8 / 57
9 / 56.5
10 / 56


Any advice?
What does it mean?


Note....twice, after revving the engine, and then turning the car off, the pressure faded fast to the low 40's....I tried to duplicate it, but it held firm the next few times.

Oh, btw, we replaced the fuel filter earlier, just forgot to mention it.

 

Couple of things....
GM does not publish any "engine running" fuel pressure specs for this engine. Just for the record, 54psi at idle is pretty common.
Key on, engine off, pump running: Your reading of 60psi is the minimum allowable. Could just be gauge error, (reading low) but your running pressure is normal, which gives no reason to question the accuracy of the gauge. Leakdown is acceptable. The only other test for fuel delivery is pump volume. It should deliver a minimum of one quart in 30 seconds, unrestricted. In other words, straight out of the pump into a jar etc. If you decide check it, you'll most likely find it to be very close to the minimum, just like prime pressure. Bottom line, I doubt fuel delivery is the problem.

Have you checked camshaft retard? It must be checked with a scan tool capable of accessing it, (obviously) Not all scan tools can access it though. If cam retard is off enough, it can cause a lack of power, misfires, and cause transmission shift points to change, along with other "issues". Spec is zero degrees + or - 2 degrees and it will not set a DTC and turn the SES light on unless it's off by more than ~25 degrees. For example, if it's off by 20 degrees in either direction, the engine will run, but engine and transmission performance will suffer, and no SES light!

 

OK, thanks for the input. What tool measures camshaft position? It it a sensor? Do you have to remove the motor? I called my local mechanic, he said I have to find an engine building shop.

 

OK...maybe a fuel volume issue.....did 4 tests, 30 seconds each, got a little over 1/2 quart in 30 seconds.

test 1 600ml gas cap off
test 2 620ml gas cap off
test 3 650ml gas cap off
test 4 650ml gas cap on

anyway, each is about 2 1/3 cups, just about half of expected value.

Could you please verify volume expectations.

Thx...

 

Camshaft retard is checked, (observed) using a scan tool. Plug in the scan tool, select the correct menu on the scan tool, idle the engine, snap throttle up to 2,000 RPM and back to idle, and read it. If it requires adjustment, loosen the distributor hold down bolt and rotate the distributor. The factory hold down bracket will allow ~10 degrees of total adjustment. If more is needed, remove the distributor, remove the OE hold down bracket and toss it, install a SBC, (small block chevy) hold down bracket. This modification makes camshaft retard fully adjustable. Most auto parts stores stock the bracket for under $5, made by Mr. Gasket... high performance chrome plated

Fuel pump volume: Actual spec is 23.28 ounces in 30 seconds. Sorry, I was off a bit Your average is ~21.5 ounces in 30 seconds. Volume is as expected, slightly low. Low volume will cause fuel starvation to the engine with the same symptoms as a restricted fuel filter: lack of power on hard acceleration and no SES light. Take into consideration that battery voltage to the pump is higher when the engine is running, which will increase both maximum output pressure and volume, it would be a real stretch to say this is the problem. We'll keep this in mind, but for now, check camshaft retard.

 

What menu item should I choose on the scan tool. Will any scan tool have these options, or do I need one with more options?

I may sound like I know what I'm doing, but I don't.

 

The el cheapo scan tools, ($300-$500) can't access it. Most any bi-directional scan tool will access it, but they start upwards of $1K for a decent used one. There are software programs you can install on your PC or lap top that will also access it. Better off finding a shop that is familiar with what camshaft retard is, what it does, and how to correctly adjust it. With the proper scan tool, (or software) it can be checked, modify the distributor, and adjust it, all in about 30 minutes.

 

Hook has it covered, as usual. I'd really look at that CMP retard.
Another indicator of low fuel delivery would be actual driving under those conditions especially at 9000 and watching fuel trims. If it's going lean at the point where it's bogging, and/or when it downshifts might be good to get a different pump.
Has the hard shift been fixed? Confused.

What I really think needs done is eliminate subjective nature of 'low power'. Help if another blazer could be test driven at same conditions. My immediate thoughts were of how aggravating it is to me that mine downshifts when I press 'increase Cruise Speed'. My Bird accels slower but rarely downshifts. 400 lbs lighter, sure but also 1/2 liter less torque.

Here's something interesting I found while researching {Yes I do that.. a lot when folks are obviously trying to help themselves}
Lose power going uphill. Engine rpm's wont go above 2,000 and no down shift - Page 2
- it's a Toyota has no power and it WONT shift when called on but otherwise pretty similar. Thing is, that should have been reflected in the long term fuel trims

All that aside, what hasnt been addressed is the possibility that the cam timing is off. I mean the cam itself. The main shortcoming of the GM method is the PCM has no idea where the cam actually is.

 

OK....she's not retarded (the blazer, I mean)....took it to a shop, did CKP correlation procedure, said it checks out for cam / crank alignment...

Next...!!!???

Is it possible that the 31" tires, brush guard, roof rack, and tow hitch are weighing it down?