In this article, I"m gonna" display you the most effective means to check the fuel pump on GM 4.3L, 5.0L, 5.7L engines with the ‘Spider’ fuel injector assembly and also it entails using a fuel push gauge. I"ve likewise included how to inspect a no fuel problem with beginning fluid (although this is no the many effective method to check the fuel pump).
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It"s to be my suffer that misdiagnosing a bad fuel pump is a common occurrence on the 4.3L, 5.0L, 5.7L GM vehicles through the ‘Spider’ fuel injector assembly. Why? This is due to the fact that in about 50% of the time, the fuel pump delivers enough fuel to keep the engine running but not sufficient to begin the engine (instead of simply frying totally and no delivering any kind of fuel at all). When this happens, you"re able to spray starting fluid (or carb spray) down the engine and it"ll start and also run (once you revolve it off, you have to spray again to acquire it started).
Yes, permit me repeat that one an ext time: together crazy as this sounds, the fuel pump will provide enough fuel to store the engine running, however not enough to start it as soon as you"re cranking the engine and also this renders a the majority of folks think that the problem lies everywhere else however in the fuel pump!
Contents the this tutorial:
NOTE: This tutorial just covers GM pickups and also SUVs equipped through the ‘Spider’ fuel injection system. Because that the fuel pump check of accelerator body fuel injected (TBI) pickups and SUVs, the adhering to tutorial will help:
IMPORTANT: due to the fact that you"ll be working approximately gasoline and/or starting fluid, it is in careful, take all vital safety precautions and also think safety every one of the time.
Which and also Where to Buy A Fuel push Gauge
Owning a fuel pressure gauge is now ending up being a must. Every vehicles now use an electrical fuel pump to supply fuel (under high pressure) to the fuel injectors and also the best means to diagnose this fuel pump is through a fuel push gauge.
In all of the GM 4.3L, 5.0L, 5.7L fitted vehicles, GM was kind sufficient to put a Schrader valve on the fuel injector rail whereby you have the right to tap into the fuel system and also check its performance.
A fuel push gauge can expense you as small as $40 (US) or as much as $200 (US). The price difference depends ~ above what type of fuel push gauge collection you buy, this means either purchase a non-professional technician grade tool or a expert technician great tool. Whichever one girlfriend buy, it"s an investment that will certainly pay because that itself numerous times over.
I"m going to evaluation two various fuel push gauge sets that will shed some light into which one is the one you might want/need come buy.
Your regional Parts house will have actually a fuel pressure gauge collection to market you, return you"ll pay more for it and also it won"t be a professional grade tool (if that"s what you"re looking for).
The ones i recommend space either the Actron CP7838 skilled Fuel push Tester or the OTC 6550 understand Fuel Injection Kit. In the next paragraphs I"ll define why.
The Actron CP7838 expert Fuel press Tester is a an excellent tool but not a skilled technician level fuel push gauge. Although the name provided by Actron to explain it has actually the native ‘professional’ as component of the name.
Why carry out I know this is a great tool? Well, I own one (I additionally have a skilled level class fuel push gauge set) and also I have actually used that in a constant manner and also I have the right to tell you that it works.
The just things ns don"t like around it is 1.) No molded situation to put the fuel press gauge and the fittings that go through it and also 2.) girlfriend can"t buy the fittings, the you may shed or break, separately. But for the price, it"s a great deal.
You"ll have the ability to test most of the GM vehicles, most Ford vehicles, amongst several makes. Back this is no that important if you"re only worried about testing her GM vehicle.
The OTC 6550 grasp Fuel Injection Kit will have the adaptors for Asian and also Domestic (USA) vehicles. So, if you occupational on cars for a living and you job-related on a selection of Makes and also Models, this is the fuel push gauge set that you need to have in your device box.
Since this fuel push gauge collection is a skilled grade technician tool, you can buy many of the components, that make up the set, separately. This comes in handy, due to the fact that you"re able come buy everything fitting you shed or gets damaged.
Also, and also probably the last consideration, is the this is one OTC tool, and OTC has been around for a long, long time and also makes a ton of automotive specialty tools well-known for quality.
TEST 1: checking The Fuel pressure Specification
The fuel device in your 4.3L, 5.0L, or 5.7L Vortec engine demands at the very least 50 PSI that fuel push to start.
The fuel pump produce much an ext than simply 50 PSI the course yet the bare minimum the engine needs to start is 50 PSI. Noþeles less and also it will certainly crank because that ever before it beginning or not begin at all.
So, the very an initial thing you have to do is come verify the the fuel pump is delivering at least 50 PSI of fuel push while the engine is cranking. Yes, if the engine is cranking.
Locate the Schrader valve on the fuel line the connects to the ‘Spider’ assembly. This is wherein you"ll attach your fuel press gauge (the first photo, in the image viewer, is that a 4.3L, and also the second of the V8 engine).
NOTE: In instance you"re wondering, the manufacturing facility manual mentions that the fuel pressure for the CSFI system should be between 56-62 PSI. The CPI system"s fuel pressure need to be between 60-66 PSI. The hands-on doesn"t clues if this press is vital on engine off, just that this pressure need to be preserved ‘under all operating conditions’.
If friend don"t understand whether you have actually a CPI or CSFI system, girlfriend can discover out the difference between them by checking out the information in this subheading: ‘Spider Fuel Injection Basics’ found in this tutorial: exactly how To check The ‘Spider’ Fuel Injector Assembly (4.3L, 5.0L, 5.7L).
OK, to get this show on the road, this is what you"ll must do:
Connect your fuel pressure gauge to the Schrader valve.Before you download the fuel push gauge, ar some rags around it and also underneath the fuel heat (in instance some fuel spills out when you connect the gauge to it).
Pressurize the fuel device by activating the fuel pump.You have the right to do this by simply turning the an essential On and also Off several times. Once the fuel pressure gauge registers pressure, check for fuel leaks about the Schrader valve.It"s really important the NO fuel leaks are current for the accuracy the the test. As soon as you have verified no fuel leaks, continue to the next step.
Have her assistant crank the engine as you eyeball the fuel pressure gauge. It"s vital that you have actually someone rather crank the car so that you have the right to eye-ball the fuel pressure gauge.
You"ll get one that two results with this test:1.) The fuel push gauge will certainly register at least 50 PSI and also the engine will begin or.2.) The fuel pressure gauge will certainly register 49 PSI or less and also the engine will Not Start.
OK, let"s find out what her fuel push gauge results mean:
CASE 1: If your fuel pressure gauge review 50 PSI or more as the engine cranked. This means that the fuel pump on your 4.3L, 5.0L, or 5.7L is OK and not the reason of your No begin Condition.
The next step is to observe the fuel press gauge"s needle (after her helper quit cranking the engine). The needle need to descend to about 40 come 45 PSI and stay there for at least 4 come 5 minutes. If the needle walk NOT continue to be at this fuel pressure (more specifically: if the needle drops come 0 PSI automatically -by automatically I median within the first 15 seconds), you have either the fuel push regulator or a fuel injector leaking fuel inside the plastic intake plenum.
You can discover the fuel push regulator check here: just how To check The ‘Spider’ Fuel Injector Assembly (4.3L, 5.0L, 5.7L).
IMPORTANT: This test result could be telling you the the PassLock anti-theft device has armed itself and also is maintaining your pick-up or SUV from starting. Ns recommend acquisition a look in ~ the adhering to section (in the following page): Difference in between A negative Fuel Pump and An Anti-Theft system (PassLock) Failure.
The adhering to tutorial may additionally be a good starting point in diagnosing the cranks but does not start condition your GM pickup or SUV is enduring (if it"s no fuel pump related): just how To Troubleshoot A No begin (GM 4.3L, 5.0L, 5.7L).
CASE 2: If her fuel push gauge walk NOT read 50 PSI or much more as the engine cranked. This means that the fuel pump is bad, also if friend spray starting fluid under the throttle body and also your automobile Starts.
If the engine does not get at the very least 50 PSI as soon as cranking, it won"t begin (and is the surest indicator that the fuel pump will go totally bad in short). If in your situation the gauge check out 45 come 49 PSI, the engine will eventually start after numerous attempts as the fuel starts to accumulate ~ above the Pistons or if girlfriend spray beginning fluid (or carb spray) into the intake.
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If the fuel push reading to be 0 PSI, then the fuel pump is most likely fried. Why ‘probably"? Well, girlfriend still need to make sure: 1.) the the fuel pump fuse and also relay room OK. 2.) the you have sufficient fuel in the tank (don"t laugh, the happens).