How to check egr?

Hey Gents,

I did a search but wasn't able to find a specific direction to go. I have a 99 Blazer with 130k on her. Its started cutting out/stumbling upon acceleration awhile back and I haven't been able to find the problem. Sometimes it doesn't idle right either. I've taken it to the local parts store where they hooked up a scan tool and have gotten tps, egr and random misfire codes. I checked the tps according to good ole Haynes and it checks out ok. The following parts are new or too new in my opinion to be bad again: fuel pump, filter, fuel press reg, air filter, plugs, wires, cap, rotor, and coil. Today it wouldn't start (no spark and no 12v at coil) I didnt know how to check the ign module but had 12v to it. I pulled the crank sensor and it was a little gummed over so I cleaned it. After puttin it back in, she started up but still stumbles. Before I have to take it in somewhere I'd like to test the egr but not sure how to, they're not like the old ones. Any advice on what to do next before I have to take it to a shop is greatly appreciated.

Keith

I can give you the test procedures, but need a little more information from you. What is the 8th character in the VIN? What were the codes, (PXXX)? Was the SES, (Service Engine Soon) light on, or were the codes in the history file? What is the fuel pressure, and what pressure does it hold when the pump shuts off?

Old Master,
Yes the Serv Eng came on yesterday. Today since I cleaned the crank sensor and drove it, it has not. I only drove a short distance though. The 8th char. is W and the codes are: history P0122, P1122, P0300 and transient P0405. As far as fuel pressure, yesterday the prime was 58psi then dropped to 56 after 2 seconds and at idle it bounced from 51 tp 57. I replaced the press. reg. and the prime stayed the same (58) then settled at about 54 at idle and didn't fluctuate like before. As far as after shutting it off I'm not sure. It set for a couple of minutes before I relieved the press to take off my gauge. I can do it again if you need me to, its sittin in the drive. Just have to go get my gauge back out of the toolbox.

Thanks
Keith

58 PSI is too low for the prime, I'm surprised it even started. Are you aware the fuel pump only runs for 2-seconds when the key is turned on, (engine off) and then the key must be off for 10-seconds before the pump will run for another 2.

The pressure will start to drop as soon as the pump shuts off. Unless you can see the gauge when the key is turned on you may not be seeing the true prime PSI.

The short distance of driving, was not enough for the PCM to run all of the monitors, guaranteed. Certain monitors may take several days to run. Each monitor has a "drive cycle" and the parameters must be met exactly, before the monitor will complete the test. Each monitor has a unique "drive cycle", so the SES light not coming on doesn't surprise me.

The DTC's P0122 and P1122 are both TPS DTC's which can cause a stumble or stall on accel. Both are for a low input and could mean an open circuit or a faulty TPS. The P0300 is "random misfire" and could be due to the fuel pump being weak. It could also mean a secondary ignition problem such as distributor cap, rotor, plug wirs, spark plugs, or ignition coil. The P0405 DTC is a low EGR input and may have been set due to the other DTC's.

The hold pressure appears to be satisfactory which means there are no leaks. The fuel pump prime psi is too low, must be 60psi MINIMUM. Idle psi is also low which means the pump is not capable of supplying a sufficient volume of fuel to the injectors. The results of your pressure test indicate the fuel pump is weak and needs to be replaced. Here is some info on fuel pump diagnosis and testing.

Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the PCM will shut off the fuel pump after approximately 2 to 3 seconds.

Fuel pressure test:
Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates a leak. The most likely place is the fuel pressure regulator, or the lines under the upper intake manifold.

Thanks for the advice guys although not what I wanted to hear. Why does this type of fuel pump not last very long. Poor design? This will be number two for this vehicle. At $500 a pop this is really disappointing. :frown: I am going to check my readings again one more time before I go to pick one up but I'm sure the outcome will be the same. I'll post the outcome. Thanks again!

Keith

I have saw a lot of them run 150K to 250K.
But proper care and service is the key.
Never run your tank low on fuel.
PEOPLE THAT DO HAVE A LOT LESS FUEL PUMP PROBLEMS.
Keep a good clean fuel filter on it.
Use good clean gas.
Bad wiring and electrical system will also kill a fuel pump.
And the use of a good OEM replacement fuel pump when it does wear out.
MT