scion7722

Driving down the road van dies and wont start again. turn the key it turns over like it its trying. service engine light has been on for acouple of days so got a code reader and checked the codes came up P0102 MAF sensor low imput.... means what??? everyone says a bad MAF wouldnt cause a no start, checked fuses, has gas, battery volts good. thought maybe fuel filter so pulled it, it rattles alot so figured it was bad, changed it and no go! Thought fuel pump, pulled fuel line by the throttle body turned key fuel spewed out... figure its good. Pulled spark plug wire checking for spark got spark at plug than at coil. nighfall came still working during one of the atempt to starts saw acouple of sparks off the wires and by the starter, found one of started wires shorted on the starter.... figure thats the prob... pull starter get checked starter good so reinstalled wrapped wires gave it a try.... no go! Pulled the air intake cover i guess its called and sprayed alittle carb cleaner in while trying to start..... it starts but dies instantly, tried acouple more times without the assistance and it started but chuggs and died again after the third attempt wouldnt start again. gave up and bought a MAF sensor installed no change. still dont know what low input is caused from. book says most commonly service soon light is connected with a EVAP system pressure loss...... ummmm ok. that helps me out none. any ideas would help out greatly its alread the end of the third day of no car because of this prob.

Blue Bowtie

Welcome Aboard!

The DTC (error code) is probably unrelated to the no-start. I didn't see the year of the vehicle, but since you have a MAF, it is likely the CPFI system from '93 or later. These systems are extremely sensitive to fuel pressure. They require a minimum of 31 PSIG to start, and 54 PSIG to remain running after start. Testing the pump by opening the line and powering it up may be a good indication of pump output FLOW, but doesn't indicate much about pressure. Changing the fuel filter is a good idea, and you are on the right track.

Your next step should be to test actual pump pressure with the system closed (reassembled). Remember, you need 61 PSIG minimum to operate teh injector poppets. Actually, I've seen a couple of them start at 58-59 PSIG, but not consistently or reliably. Once you determine fuel pressure, you can continue your diagnosis from there.

If you determine the pressure is low, that doesn't necessarily mean a failed pump. These pumps are very sensitive to voltage, and there are no fewer than four connections right near the pump and tank, let alone the connections near the relay and front of the vehicle. Any one of them that may be weak could be killing fuel pressure. No more than a one volt drop to the fuel pump anywhere in the circuit can be enough to decrease pressure below the minimum for operating the injectors.

As a matter of fact, if you suspect this is your problem, try jump starting from a running vehicle. The higher charging voltage of the running vehicle may be just enough to allow the pump to produce adequate pressure and start the engine.

scion7722

Thanks for the reply. I tried to jump it but it didnt work. how would one go about checking the fuel pressure? I call autozone and they said they dont know of any fuel pressure guages for a 97 or anything that would work.

Blue Bowtie

My standard fuel pressure gaige works fine. It is the same type used on other GM MPFI, TPI, and LT1 systems - 7/16" - 20 thread pitch, 0-100 PSIG.

jimmypodunk

Your Autozone isn't very smart. Go to the TOOL SECTION and get a generic fuel pressure guage that connects to the schrader valve under the dog house. Get a Haynes repair manual too while your at it if you're not sure where to hook it up.

__________________
Ruh Roh George!

drew300

My '97 developed difficult starting. It turned out to be a weak fuel pump.
It would start with a spray of starting fluid, and keep running fine.
I borrowed a guage. My cranking fuel pressure was 59 lb. I phoned GM, and the service said "minimum 60" . I said I have 59 lb, and the rep said "minimum 60". I replaced the pump, but also returned the guage. It works just fine now.
BTW: according to Hayes manual, these need more pressure to start than to run. I recall about 66 psi to start, with running varying, as low 55 psi.
I'd try the starting fluid. If it start well, at least you know the ignition if good.
Also, replace the fuel filter. That's cheap insurance in case it's plugged.

scion7722

well I got a pressure guage, turned key on it read under 10 psi. bought a pressure regulator noticed that there is vacum port but no line anywhere. Is there supposed to be one? Where would it connect to i dont see any other ports.

Blue Bowtie

No separate vacuum line is provided or required, even though the regulator has a fitting for a hose:




Since the regulator is mounted to the fuel injector control block, it is within the upper plenum, subjected to manifold vacuum all the time.




And on the engine:

scion7722

Wow thanks alot for the info and pics! I also noticed on the manifilod (intake cover piece) there is a valve/solonoid that has a hose that connects to i believe the pcv. the valve/solonoid also has a vaccuum port on it, does it need a hose? Well i am assuming that since the regulator didnt fix it the last option is the pump right???? or maybe the check valve? but if the check valve was stuck open than there would be no pressure build up......right not low pressure

scion7722

Well it turns out it was the pump, after ofcourse i changed everything else but that. but hey it preventive maintenace right!!!!! Thanks for all your help.