Hello,



I’m new here. I’m from Germany working in the US at the moment and I own a 1999 Blazer.



It stoped running last week and I can’t startet it any more, I changed the distributer, Fuel filter and checked the fuel pressure.

Turing the ignition on, the fuel pressure shows instantly 62PSI (drops in a second down to 58PSI: after 5min it drops down to 54PSI and after 10min its at 51PSI)

When I try to start (cranking) the engine it will fire up for about 1-2sec. But the Fuel pressure drops down with the crank for the startup to 38PSI, which instantly shuts the engine down. (after the mentioned 1-2sec)



my question is, what is the most likely cause? Is it the fuel pump or the pressure regulator or …??



thanks for your help.

 

So it starts up and runs but the fuel pressure drops to 38 psi and the engine quits or the fuel pressure is 38 psi during cranking and it cranks but wont start/run?

George

 

It starts up for 1second because - before cranking it has 58PSI (I think it holds the pressure right in front of the “injection spider” wich is good enough for a 1second startup) - but with the cranking it went down to 38PSI. And the engine don’t run further.

I made a new discovery: I measured the pressure right after the fuel filter. It indicates 60PSI when switching on the ignition, but went down very quick to low pressure below 30PSI. And when cranking it just holds 40PSI there as well, at this spot.

After reattaching the fuel filter, the new filter was dripping on the rear connection to the fuel line. Though I put on the old filter again, wich than gave me a 48PSI (max output) at the fuel pressure measuring point at the engine.

I now ordered a new fuel pump. (And a new filter)
that’s the most likely cause of failure.
my opinion.

thanks for any advise.

 

I changed the fuel pump, and the Blazer started up but on 5 Zylinders only… and tried very hard to start up.
Black smoke came out of the exhaust.
Additionally smoke came out of the area of bank 1, could be exhaust gases or all the fluids wich ran over during repair while warming up.

I’ll check the compression (especially Bank 1) next. And if the compression is good, I think I’ll change the injection spider.

Any other thoughts? Or any Tips?

 

So it started or it tried to start?

What are your fuel pressures now?

How do you know that it only ran on 5 cylinders?

Where near bank 1 did smoke come out?


George

 

I think the smoke on bank no1 was only old oil from the repair process. Due to the whole issue I change the intake gaskets.

I testet the compression today, all cylinders except from No.3 (can’t test it because of the steering column in the way) are ok (165-175PSI).

And after checking all ignition cables and readjusting them, the Engine starts up.

It runs kind of smooth, spits a bit due to the fact of the work and try’s the last weeks.

But one important fact, it seems to run a bit rich, because it starts very hard. After startup black smoke will come out of the exhaust.
And after the engine warms up it won’t start up again or only with full throttle after a while.
Could it be possible, that I need a new injection spider (maybe the injectors of the old spider are bad, I try to clean them last week) due to the higher pressure of the new fuel pump.

Thanks for your recommendations…

 

I recommend that you repeat the fuel pressure test.

Do you have a scanner that can monitor live data such as fuel trims?



George

 

Unfortunately not. Just a pressure gauge:
Pressure while the engine is running is 74PSI, the engine still stutters, when running in Idle (stutter worst at ~1200RPM). When it stutters the Pressure rises in a split of a second up to 90PSI.

The car stopped 3 weeks a go while I was on a highway, without any warning. The engine just quits working.
Before since I had it it always had the P0420 fault, and I changed the O2 sensor but in Converter into a P0135 code (faulty O2 sensor) though I put the original back in.

If I pull the spark plugs, they are black and sooty, even with fuel on them. Out of my opinion it runs to rich.

I’m not sure whether it is something more catastrophic, I might have to check whether the coolant fluid can hold pressure - maybe cylinder head gasket? I can’t see any whit smoke so far…

I really don’t know and start to reach the limits of my toolbox here. I’ve more tools in Germany but they won’t help me here.

thanks for your advises.

 

Those fuel pressures are way too high, it sounds like you may have a failed fuel pressure regulator or a restricted return line and yes black sooty plugs is running very rich as you suggest. What is the history on the fuel injector spider and regulator?


George

 

Well,
injection spider was as well my next suggestion.

what is the normal pressure? 60PSI?

History:
I bought the car in April after I moved from Germany to the US. To keep it for the time I’m her - until October.

The fuel spider looks pretty old, there was no leak on the pressure regulator - can’t see the bare metal underneath (wich will be a typical indicator from dripping fuel)

well, than a new injection spider (including pressure regulator) will be ordered…

thanks for the recommendation.